Experimental and Theoretical Study of Hyperfine Coupling of Vanadocene Complexes

UNIVERSITY OF PARDUBICE FACULTY OF CHEMICAL TECHNOLOGY DEPARTMENT OF GENERAL AND INORGANIC CHEMISTRY

EXPERIMENTAL AND THEORETICAL STUDY OF HYPERFINE COUPLING OF VANADOCENE COMPLEXES

Annotation of the PhD Degree Thesis

AUTHOR: Ing. Jan Honzíček SUPERVISOR: Doc. Petr Nachtigall, PhD.

2005

- 1 -

The PhD degree Thesis was carried out at Department of General and Inorganic Chemistry of University of Pardubice in years 2002-2005.

Candidate: Ing. Jan Honzíček

Reviewers:

The PhD Thesis will be defended at University of Pardubice in face of Commission for Defending Doctoral Thesis chaired by...... on...... 2005.

The PhD Thesis will by available to those interested in the central library of University of Pardubice.

- 2 - 1. Introduction

Metallocene complexes of the type Cp2MX2 (M = early transition metal; X - halide, pseudohalide) are currently largely investigated due to their biological [1, 2] and catalytic activity [3, 4]. Currently known studies show that such activity is closely connected with the metallocene complex structure [5, 6]. X-ray structure analysis and spectroscopic methods are useful for the structure investigation. X-ray analysis can be used only for single crystals of the compounds. The isolation of the compounds in the solid state and preparation of the single crystal is sometimes very is difficult or impossible. Therefore spectral methods are often used for structure investigation. NMR spectroscopy cannot be used for paramagnetic compounds therefore the interpretation of vibration spectra are in point of the interest. Infrared and Raman spectra give important information about the structure of the metallocene complexes. Based on such methods it is possible to find out the presence of the metallocene fragment with two η5-bonded cyclopentadienyl rings [7]. This work is attended especially for the study of vanadocene complexes by EPR 51 7 spectroscopy. The presence of the magnetic active nucleus ( V, I = /2, 99,8 %) causes the hyperfine coupling (HFC) that is very sensitive to changes in the coordination sphere of the central metal. Some problems occurs with the assignment of the obtained EPR parameters to the concrete species, when the particular structure is not known from another experimental technique. Such problems can be solved by theoretical calculations. Recently, EPR parameters of some 3d-metal compounds were theoretically investigated at the DFT level of the theory [8-12].

- 3 - 2. Results and Discussion

2.1 Synthesis and Vanadocene Complexes

Metallocene complexes of the type Cp2VX2 and Cp'2VX2 (X = NCO, NCS, N3, CN, 5 5 dca, tcm, dcnm; Cp = η -C5H5, Cp' = η -CH3C5H4, Scheme 1), were prepared by reaction of vanadocene dichloride with the large excess of the sodium or potassium salt of the corresponding pseudohalide.

R R Cl X V + NaX (KX) V + NaCl (KCl) Cl X R R

1a: R = H 2a: R = H X = NCO 2b: R = CH3 X = NCO 1b: R = CH 3a: R = H X = NCS 3 3b: R = CH3 X = NCS 4a: R = H X = N3 4b: R = CH3 X = N3 5a: R = H X = CN 5b: R = CH X = CN 6a: R = H X = dca 3 6b: R = CH X = dca 7a: R = H X = tcm 3 7b: R = CH X = tcm 8a: R = H X = dcnm 3 8b: R = CH X = dcnm 3

Scheme 1 Synthesis of pseudohalide complexes.

Monosubstituted derivatives (Cp2VClX) are formed by ligand-exchange reaction. The EPR spectra measurements show that all prepared complexes are contaminated with disubstituted compounds (Scheme 2). Only complex Cp2VCl(tcm) (7c) was successfully separated from complex 7a by extraction, because these complexes show very different solubility in organic solvents.

Cl Cl tcm V + Na(tcm) V + V +NaCl Cl tcm tcm

1a 7c 7a

Scheme 2 Reaction of complex 1a with Na(tcm).

- 4 - Complexes of carboxylic acids Cp2VX2 a Cp'2VX2 (X = OOCH, OOCCCl3, OOCCF3; 5 5 X2 = (OOC)2, (OOC)2CH2; Cp = η -C5H5, Cp' = η -CH3C5H4; Scheme 3), were prepared by reaction of vanadocene dichloride with corresponding carboxylic acid.

R1 O R1 9a: R = H R = H R2 1 2 RCOOH O 10a: R = H R = CCl Cl 1 2 3 V V + HCl Cl O 11a: R1 = H R2 = CF3 R 2 9b: R = CH R = H R 1 3 2 1 R O 1a: R = H 1 10b: R1 = CH3 R2 = CCl3 11b: R = CH R = CF 1b: R = CH3 1 3 2 3 HOOC A COOH

R 1 O 12a: R1 = H A = O 13a: R = H A = CH V A 1 2 O 12b: R1 = CH3 A = O 13b: R = CH A = CH R 1 3 2 1

Scheme 3 Synthesis of carboxylic acid complexes

2.2 X-ray structures

The structures of the complexes Cp'2V(NCO)2 (2b), Cp2V(NCS)2 (3a), Cp2V(N3)2 (4a),

Cp2V(dca)2 (6a), Cp'2V(dca)2 (6b), Cp2VCl(tcm) (7c), Cp'2V(dcnm)2 (8a),

Cp2V(OOCCCl3)2 (10a), Cp'2V(OOCCF3)2 (11b) and Cp2V(OOC)2 · 0.5(COOH)2 (12a) were determined by X-ray diffraction analyses. Complexes have typical bent metallocene structure with two η5-bonded Cp (Cp') rings and two donor atoms of other ligands around the vanadium(IV) center. The substitution of chloride ligands does not change the geometric parameters of the vanadocene moiety (Cg- V 1.95-1.98 Å, Cg-V-Cg 133-136°). 1,1'-dimethyl substituted complexes show different location of methyl groups. Complex

Cp'2V(NCO)2 (2b) has one methyl group bellow the X–V–X moiety and the second one at the side (Fig. 1a). Complexes Cp'2V(dca)2 (6b) and Cp'2V(dcnm)2 (8b) have methyl groups above and bellow the X–V–X moiety (See Figs. 2b and 3b, respectively). The methyl groups of the compound Cp'2V(OOCCF3)2 (11b) are positioned at the opposite sides of the molecule, directed away from each other (Fig. 4b).

- 5 -

a) b)

C1 C2 C16 C12 C5 C4 C13 C11 S1 C11 C3 N1 C15 O1 V1 C14 N1 C1 V1 N2 C7 C25 S2 C12 N2 C2 O2 C6 C24 C21 C10 C8 C23 C9 C22 C26

C6 C7

N6 C10

N5 C9 C8

N4 N1 V1 N2 N3

C3 C5 C1 C2

Fig. 1 X-ray structure of the complexes: a) Cp'2V(NCO)2 (2b); b) Cp2V(NCS)2 (3a); c) Cp2V(N3)2 (4a).

The results of X-ray structure analyses show that pseudohalide ligands are bonded via nitrogen atom to the vanadocene moiety in compounds 2a, 3a a 4a (Fig. 1). The bond distances V–N were found in narrow range from 2.03 to 2.08 Å.

Complexes Cp2V(dca)2 (6a) and Cp'2V(dca)2 (6a) have both bent dca ligands bonded via terminal nitrogen atom (V–N = 2.04 - 2.05 Å). The geometry of dca ligands are affected by coordination to vanadium(IV). Although the coordinated and non-coordinated C≡N bond lengths is the same (1.145(3) - 1.157(2) Å), the N–C bonds beside coordinated cyano-groups are significantly shorter ([1.286(3) - 1.301(3) Å] than beside non- coordinated groups [1.308(3)-1.322(3) Å]. Such distortions can be explained by two possible resonance structures, see Scheme 4.

- 6 - a) b)

N10

N10 C9 C25 C24 C22 C26 C9 C23 C21 N8 N8 C25 C7 C21 N6 C7 C23 N6 C22 C24 V1 V1 N5 N1 C13 N1 C4 C2 C14 C2 N3 C12 C13 N3 C4 C15 C11 N5 C14 C11 C15 C12 C16

Fig. 2 X-ray structures of the complexes: a) Cp2V(dca)2 (6a); b) Cp'2V(dca)2 (6b).

O- O- N N N N

N N

N N O- O- N N

N N

N N O- O O O- N N

N N

Scheme 4 Resonance structures of non-linear pseudohalides.

The unit cell of the compound Cp2VCl(tcm) 7c consists of four crystallographically independent but essentially the same molecules. One of them is shown in the Figure 3a. The planar tcm ligand is bonded to the vanadocene moiety through the nitrogen atom. The bond distances V–N (2.054(3) - 2.071(4) Å) are comparable with dca compounds 6a and 6b. The geometry of planar tcm ligand shows significant distortions that can be explained in similar way as for dca complexes. Two possible resonance structures are depicted in Scheme 4. The contribution of second resonance structure causes significant contraction of C-C bonds that are beside coordinated cyano-groups (C-C = (1.387(6) - 1.400(6) Å). The C-C bond that are positioned beside non-coordinated cyano-groups were found in the range

- 7 - from 1.399(8) to 1.1414(6) Å. The bond distances of the cyano-groups are not affected by coordination (C≡N = 1.144(6) to 1.159(5) Å).

a) b)

C8 C48 C49 C6 C7 N42 C9 C2 C1 N3 C410 N1 C47 C46 C413 C3 C5 C4 O1 C412 V1 V4 Cl4 N41 C411 O1a C41 C45 C414

C44 C43 C42 C43

Fig. 3 X-ray stuctures of the complexes: a) Cp2VCl(tcm) (7c); b) Cp'2V(dcnm)2 (8b).

Complex Cp'2V(dcnm)2 (8b) have two planar dcnm ligands bonded via oxygen atoms of nitroso groups to the Cp'2V moiety (V–O = 2.035(1) Å, O–V–O = 74.78(5)°). The dcnm ligands were found in one plane with vanadium atom (Pldcnm-PlO1VO1a = 4.81(5)°).

a) b)

C4 C5 C6 C3

F2A C1 C2 C1 F1A C5

C2 C8 F3A V1 O1 C4 C7 O1' C3

O1 V1

O2 C6 C7 O1' Cl3 O2

Cl2

Cl1

Fig. 4 X-ray structure of the complexes: a) Cp2V(OOCCCl3)2 (10a); b) Cp'2V(OOCCF3)2 (11b).

Complexes 10a and 11b have two monodentate carboxylic acids bonded to the vanadocene moiety (V–O1 ~ 2.03 Å; V···O2 ~ 3.5 Å). The bond lengths C–O (~ 1.26 Å) and C=O (~ 1.21 Å) of the coordinated carboxylic acid correspond with the monodentate bonding mode.

- 8 - Complexes 10a and 11b show different values of the O–V–O bond angle (10a: 77.6°; 11b: 89.7°). This one is evidently caused with different conformation of carboxylic acids. Unlike the complex 10a, in which the carbonyl oxygens of the coordinated COO group are pointed apart, in the case of the compound 11b these oxygens are pointed towards the

O–V–O angle (Fig. 4). Such differences manifests in different dihedral angles O1'–V–O1–C (10a: 179.7°; 11b: 38.2°). Complex of the oxalic acid (12a) forms a chelate. The bond distances V–O (2.02 Å) and bond angle O–V–O (78.6°) are very similar to values found for complex 10a. The compound 12a is a dimer in the solid state with two molecules of the complex connected via oxalic acid bridge (Fig. 5).

C8 C9 C7

C10 O5 C6 O1 O3 C11

V1 C13

C3 C12 O2 O4 C2 C4 O6 C1

Fig. 5 X-ray structure of complex Cp2V(OOC)2 · 0,5 (COOH)2 (12a). The second part of solvate is related by center of symmetry. Hydrogen bond is drawn as dashed line (O6···O4 2.586(1)Å, O6-H6A···O4 178(2)°).

2.3 EPR spectra

The EPR spectra were measured for prepared complexes (2-13). The majority of the pseudohalide complexes (2-4, 6-8) show similar values of the parameters |Aiso| a giso (see

Tab. 1). Only cyanide complexes 5a and 5b give the |Aiso| values much lower and giso higher than the other vanadocene complexes. This one is caused by strong electron withdrawing effect of the cyanide ligands. The decreased value of the |Aiso| constant is caused by larger delocalization of the unpaired electron on the pseudohalide ligands.

- 9 - Table 1 EPR parameters of the pseudohalide complexes.

|Aiso| [MHz] giso |Aiso| [MHz] giso 2a 212.2 1.9818 2b 212.5 1.9820 3a 205.3 1.9844 3b 205.3 1.9844 4a 199.7 1.9827 4b 198.9 1.9804 5a 169.8 1.9948 5b 169.0 1.9944 6a 210.5 1.9844 6b 211.3 1.9841 7a 206.3 1.9840 7b 207.6 1.9845 7c 206.5 1.9836 8a 209.3 1.9810 8b 208.1 1.9817

Complexes of monocarboxylic acids 9-11 show very similar EPR parameters (|Aiso| ~

220 MHz, giso ~ 1.98, |Ax| ~ 240 MHz, gx ~ 1.99, |Ay| = ~ 360 MHz, gy ~ 1.95, |Az| ~ 60

MHz, gy ~ 2.00). It is evident that substitution of on monocarboxylic acid does not affect either A-tensor or g-tensor. Dicarboxylic acids complexes, presumable chelates, show some differences in A-tensor.

The parameters |Aiso| and |Ay| are much lower than were found for monocarboxylic acid complexes. The values of these parameters increase with increased number of chelate ring members.

Table 2 EPR parameters of carboxylic acid complexes.

|A | |A | |A | |A | iso g x y z g g g [MHz] iso [MHz] [MHz] [MHz] x y z 9a 220.3 1.981 236.5 368.8 55.7 1.988 1.956 2.000 9b 220.8 1.981 245.2 358.7 58.5 1.986 1.952 2.006 10a 221.1 1.981 237.2 366.3 59.9 1.987 1.956 2.005 10b 222.2 1.980 249.0 356.2 61.4 1.988 1.952 2.001 11a 222.2 1.981 241.7 367.2 57.8 1.987 1.953 2.003 11b 222.5 1.981 250.3 357.3 59.9 1.985 1.952 2.007 12a 189.8 1.984 241.8 307.1 20.4 1.995 1.961 1.997 12b 190.8 1.984 240.5 308.7 23.2 1.990 1.963 1.999 13a 208.1 1.981 255.0 334.1 35.0 1.984 1.959 2.001 13b 207.6 1.981 248.2 335.2 39.7 1.984 1.957 2.003

Bis(cyclopentadienyl)vanadium(IV) complexes (series a) and their 1,1' dimethyl substituted counterparts (series b) show very similar values of both A-tensor and g-tensor. So, such substitution does not significantly affect the EPR parameters.

- 10 - 2.4 Calculations of HFC tensor

EPR spectroscopy is the efficient method for experimental study of d1-vanadocene compounds. The main problem of this method is the assignment of the hyperfine coupling tensor (HFC) to a particular structure of the complex when the structure is not known from the other experimental techniques. These reasons make for theoretical calculations of HFC tensor. The complexes of bio-ligands with nitrogen and oxygen donor atom (such as nucleic acids, amino acids etc.) play important role in the research of the biological activity of the transition metal complexes. Particularly, neutral and cationic complexes with such donor atoms were included into this study. + Br O V V A 15 OAO=acac Br O 16 OAO=hfpd 17 OAO=trop 14 15 - 17 18 NAN=bpy 2+ + 19 NAN=phen 20 OAN=gly N O 21 OAN=ala V A V A 22 OAN=val N N 18, 19 20 - 22

2.4.1 HFC tensor of vanadocene dichloride

Within the first order approximation the Aiso is determined by the contribution from singly occupied MO (SOMO) and by the spin polarization of other orbitals, the core s orbitals on vanadium in particular. It is now well understood that the various exchange- correlation functionals give rather different values of Aiso [8]. The calculations on vanadocene dichloride (1a) employing various exchange-correlation functionals (summarized in Table 3) show very similar trends as observed for other transition metal compounds [8, 12]. With increasing amount of exact (Hartree-Fock) exchange mixed into the exchange part of functional the Aiso constant becomes smaller. Absolute values of Aiso increase in order:

- 11 - 2 〈S 〉 increases with the increasing mixing of exact exchange into the functional. The Aiso dependence on the correlation part of functional is much less pronounced, increasing in order:

|Aiso(LYP)| < |Aiso(P86)| < |Aiso(PW91)|.

Table 3 HFC tensors (in MHz] of complex 1aa calculated at the DFT level with various functionals.

2 b Aiso Tx Ty Tz 〈S 〉 BLYP -107.1 -9.7 -128.6 138.2 0.7655 BP86 -119.1 -9.5 -125.2 134.6 0.7664 BPW91 -124.8 -9.5 -125.1 134.6 0.7680 B3LYP -140.0 -9.9 -136.2 146.1 0.7833 B3P86 -154.4 -9.7 -133.2 142.9 0.7854 B3PW91 -159.9 -9.6 -132.9 142.5 0.7881 BHLYP -189.1 -7.5 -133.0 140.5 0.8539 BHP86 -210.5 -7.5 -130.8 138.3 0.8544 BHPW91 -219.3 -7.2 -129.7 136.8 0.8644 exp. -207.2 -11.0 -140.0 151.0 --

a X-ray geometry [13]. b The spin contamination is reflected in the deviation of the 〈S2〉 from the ideal value for a doublet ( 0.75).

The best agreement between experimental and calculated Aiso is found for BHP86 exchange-correlation functional (-207 and -211 MHz, respectively). However, all calculations with BH exchange functional show the value of 〈S2〉 greater than 0.85. It is apparent that calculated values of Aiso correlate with the spin-contamination. Among the functionals employing the B3 exchange, that includes the smaller amount of exact exchange, the B3PW91 gives Aiso closest to the experimental value (-160 MHz). The agreement is significantly worse than found for BH exchange functional; however, the spin-contamination is severally reduced (〈S2〉 = 0.79). The results obtained with purely DFT description of electron exchange (B functional) show the smallest spin- contamination, however, the agreement with experimental Aiso is worse (over 80 MHz error). It remains to be seen whether such large spin-contamination is realistic and whether these functionals can reproduce Aiso for other vanadocene derivatives. Therefore, the calculations on other complexes were performed with only two exchange-correlation functionals: (i) BHP86 functional that gives Aiso in fair agreement with experiment without any scaling but it shows relatively large spin-contamination and (ii) B3PW91 functional that shows only modest spin-contamination.

- 12 - 2.4.2 HFC tensor of vanadocene compounds (X-ray geometries)

Part of the error in Aiso calculations can be due to the discrepancies between optimised and experimental geometries. In order to evaluate the ability of DFT to predict HFC tensor, the calculations on fourteen vanadocene complexes in experimental geometries are known were carried out. The isotropic and anisotropic components of HFC tensors calculated at the experimental geometries using BHP86 and B3PW91 exchange-correlation functionals are summarized in Table 4. The BHP86 functional gives value of Aiso in relatively good agreement with experiment, with the errors from –21 to +0.1 MHz. Although, significantly less satisfactory agreement was found for B3PW91 functional, this error is relatively constant.

Table 4 HFC tensors (in MHz) calculated with B3PW91 and BHP86 functionals at X-ray geometries.

b 2 Aiso(calc) Aiso(exp.) Tx(calc) Ty(calc) Tz (calc) 〈S 〉 1a a B3PW91 -159.9 -207.2 -9.6 -132.9 142.5 0.7881 BHP86 -210.5 -207.2 -7.5 -130.8 138.3 0.8544 2b B3PW91 -167.1 -212.5 -24.2 -125.6 149.8 0.7808 BHP86 -218.7 -212.5 -19.8 -125.3 145.1 0.8345 3a B3PW91 -154.6 -205.3 -16.8 -123.1 139.9 0.7775 BHP86 -206.3 -205.3 -1.8 -137.3 139.1 0.8245 4a B3PW91 -158.2 -199.7 -34.9 -117.6 152.5 0.7817 BHP86 -200.2 -199.7 -32.1 -121.7 153.8 0.8225 6a B3PW91 -163.7 -210.5 -18.0 -123.9 141.9 0.7817 BHP86 -222.8 -210.5 -13.0 -122.9 135.9 0.8465 6b B3PW91 -165.6 -211.3 -35.5 -111.2 146.7 0.7832 BHP86 -225.1 -211.3 -28.1 -112.5 140.6 0.8470 7c B3PW91 -158.6 -207.6 -12.5 -127.1 139.6 0.7826 BHP86 -213.0 -207.6 -9.1 -128.5 137.6 0.8402 8b B3PW91 -165.3 -208.1 -28.8 -119.6 148.4 0.7904 BHP86 -208.0 -208.1 24.5 114.9 139.3 0.8813 10a B3PW91 -175.5 -221.1 -13.9 -134.4 148.3 0.7841 BHP86 -229.2 -221.1 -13.6 -125.5 139.1 0.8496 11b B3PW91 -175.2 -222.2 -28.2 -123.6 152.0 0.7882 BHP86 -231.6 -222.2 -22.1 -117.8 139.9 0.8647 12a B3PW91 -147.3 -189.8 -56.0 -101.4 157.4 0.7818 BHP86 -196.9 -189.8 -50.1 -100.8 150.9 0.8321 15 b B3PW91 -164.7 -208.9 -39.2 -115.7 154.9 0.7844 BHP86 -218.7 -208.9 -30.1 -111.1 141.2 0.8541 18 c B3PW91 -142.8 -183.1 -33.3 -110.6 143.9 0.7888 BHP86 -204.1 -183.1 -24.9 -99.5 124.4 0.8790 19 c B3PW91 -147.5 -187.8 -28.0 -115.4 143.4 0.7880 BHP86 -206.9 -187.8 -21.0 -105.6 126.6 0.8704

X-ray geometries were taken from: a [13], b [14], c [15].

- 13 - Correlation of calculated and experimental Aiso is presented in Fig. 6 for both functionals. Aiso calculated at B3PW91 level using experimental structures correlate well with experimental values:

Aiso(exp) = 1.14 Aiso(B3PW91) – 22.11 (1) with the correlation coefficient R = 0.970 and standard deviation SD = 2.94.

Significantly worse correlation between Aiso experimental and calculated at the BHP86 level was found:

Aiso(exp) = 0.89 Aiso(BHP86) – 14.44, with R = 0.834 and SD = 6.67.

Evidently, the B3PW91 functional gives Aiso with error of about 40 MHz. However, this error is predictable and it depends on Aiso linearly. This error can be corrected using the equation (1). In further discussion we will use the results obtained with B3PW91 functional corrected according to equation (1).

Fig. 6 Correlation of experimental and theoretical Aiso constants, calculated with BHP86 at X-ray determined geometries (■) and with B3PW91 functional at X-ray (+) and B3PW91 geometries (○).

2.4.3 HFC tensor of vanadocene compounds (optimised geometries)

For EPR spectra interpretation of complexes, which X-ray parameters are not available, it is possible to use only optimised geometries. Thus, the geometries obtained at the DFT

- 14 - level are used in HFC tensor calculations. To show the effect of the use of the optimised geometry instead of the experimental geometry the Aiso calculated at optimised geometries are also shown in Figure 6. Small deterioration of correlation was observed: R = 0.914 and SD = 4.89. A reasonable agreement between experimental and DFT geometries was found. The differences in bond lengths do not exceed 0.07 Å and differences in valence angles are smaller than 5o. The largest difference between experimental and theoretical geometries was found for complexes 6a, 6b and 12a. Such complexes also show the largest difference between Aiso calculated at experimental and theoretical geometries.

Fig. 7 Comparison of experimental and scaled Aiso constants of vanadocene complexes at B3PW91 optimised geometries.

Experimental and calculated HFC tensors (B3PW91 level) for all 27 compounds are compared in Table 5. Both, calculated Aiso and Aiso scaled according to equation (1)

(Aiso(scal)) are reported. Very good agreement between experimental and scaled Aiso was found, with the largest deviation 9 MHz. This is depicted in Figure 7 (correlation coefficient R = 0.949 and SD = 4.51 MHz). A good correlation is consistent with relatively constant spin-contamination found for all compounds (spin-contamination in the range 0.024-0.041). A reasonable agreement between experimental and calculated (no scaling applied) anisotropic part of HFC tensor was found.

- 15 - Table 5 Comparison of experimental HFC tensors and those calculated at B3PW91 level at the B3PW91 optimised geometries (in MHz).

a 2 b Aiso(calc) Aiso(scal) Aiso(exp) Tx(calc) Ty(calc) Tz(calc) Tx(exp Ty(exp) Tz(exp) 〈S 〉 ref. 1a -159.9 -204.4 -207.2 -2.2 -138.1 140.3 -11.0 -140.0 151.0 0.7845 [16] 2a -164.3 -209.4 -212.2 -10.8 -135.4 146.2 -7.8 -145.8 153.6 0.7780 2b -164.6 -209.8 -212.5 -15.3 -128.6 143.9 ------0.7782 3a -152.6 -196.1 -205.3 -5.1 -130.2 135.3 ------0.7781 4a -157.5 -201.7 -199.7 -14.7 -126.4 141.1 ------0.7775 5a -133.5 -174.3 -169.8 -3.0 -128.3 131.3 ------0.7735 6a -157.8 -202.0 -210.5 -10.3 -128.1 138.4 ------0.7790 6b -159.6 -204.1 -211.3 -18.6 -121.6 140.2 ------0.7791 7a -156.7 -200.7 -206.3 -15.2 -119.4 134.6 ------0.7836 7c -158.3 -202.6 -207.6 - 8.2 -129.7 137.9 ------0.7820 8a -166.6 -212.0 -209.3 -12.4 -134.0 146.4 ------0.7841 8b -164.2 -209.3 -208.1 -28.8 -119.6 148.4 ------0.7904 9a -172.2 -218.4 -220.3 1.7 -145.4 143.7 -16.2 -148.4 164.6 0.7819 10a -174.1 -220.6 -221.1 -2.7 -141.3 144.0 -16.1 -145.1 161.2 0.7837 11a -173.9 -220.4 -222.2 -3.6 -140.8 144.4 -19.4 -145.0 164.4 0.7839 11b -173.2 -219.6 -222.5 -12.3 -131.5 143.8 -27.8 -134.8 162.6 0.7832 12a -151.8 -195.2 -189.8 -55.8 -102.8 158.6 -52.0 -117.3 169.4 0.7800 13a -166.2 -211.6 -208.1 -50.8 -109.9 160.7 -47.0 -126.0 173.0 0.7790 14 -154.7 -198.5 -189.5 -0.8 -136.8 137.6 ------0.7897 [17] 15 -164.7 -209.9 -208.9 -41.9 -112.7 154.6 -34.0 -129.9 163.9 0.7863 [18] 16 -163.7 -208.7 -209.9 -38.4 -112.5 150.9 -30.0 -131.9 161.9 0.7889 [18] 17 -146.0 -188.6 -182.9 -54.9 -101.4 156.3 ------0.7849 [19] 18 -143.6 -185.8 -183.1 -33.5 -109.7 143.2 ------0.7914 [15] 19 -150.2 -193.3 -187.8 -27.1 -114.7 141.8 ------0.7912 [15] 20 -143.0 -185.1 -187.6 -53.2 -99.3 152.5 -42.6 -120.2 162.8 0.7844 [20] 21 -143.7 -185.9 -187.3 -52.9 -99.7 152.6 -44.2 -119.0 163.2 0.7841 [20] 22 -143.7 -185.9 -188.1 -53.1 -99.6 152.7 -43.2 -120.2 163.4 0.7842 [20]

a b Aiso parameters scaled according to Eq. (1). References of the experimental HFC tensors.

- 16 - 2.4.4 Using of HFC tensor calculations for structure investigation

Good agreement between experimental and calculated anisotropic components of HFC tensor and excellent agreement between scaled and experimental Aiso justify the use of DFT in interpretation of experimental HFC tensor of vanadocene complexes. Several examples are shown below.

a) Acidoligand substitution

Cl Cl OOCH V V V Cl OOCH + OOCH

1a 9c 9a

EPR spectra obtained after partial precipitation of Cl- ions from aqueous solution of vanadocene dichloride (1a) and formic acid, evaporation and dissolution in inert solvent

(CH2Cl2) are superposition of simple eight-line spectra of reactant (1a) two other vanadocene compounds. Based on calculations it is possible to assign the Aiso parameters -213.5 and -

220.3 MHz to compounds 9c and 9a, respectively. The calculated Aiso constants (9c: Aiso(scal)

= 210.1 MHz; 9c: Aiso(scal) = 218.4 MHz) are in good agreement with experiment. Such calculations proved the expectation that monosubstituted compound (9c) gives the EPR parameters, which are the mean value of these for corresponding disubstituted compounds (1a and 9a).

b) Donor atom assignment

NCO OCN V V NCO OCN

2a 2a 1 2 Several structures can be expected, when vanadocene forms a complex with ligands, where more than one donor atom can form a bond with vanadium. Such situation occurred for OCN-, dca and dcnm ligands. Cyanatane can be bonded either through oxygen or nitrogen can be a donor atom. Structure

2a1 is energetically more stable than structure 2a1 at the B3PW91 level (195 kJ/mol).

17 Calculated values of Aiso(scal) (-209.4 MHz) of structure 2a1 is in very good agreement with experimental value (-212.2 MHz).

Table 6 HFC tensors (in MHz) of pseudohalide complexes.

2 Aiso(calc) Aiso(scal) Aiso(exp) E(kJ/mol) 〈S 〉 2a1 calc. -164.3 -209.4 -- 0 0.7780 2a2 calc. -185.9 -234.0 -- 195 0.7888 2a exp. -- -- -212.2 -- -- 6a1 calc. -157.8 -202.0 -- 0 0.7790 6a2 calc. -161.0 -205.7 -- 98 0.7873 6a exp. -- -- -210.5 -- -- 8a1 calc. -151.5 -194.8 -- 111 0.7823 8a2 calc. -166.6 -212.0 -- 0 0.7841 8a exp. -- -- -209.3 -- --

For dca and dcnm ligands were proposed structures with ligands bonded through cyano nitrogen (6a1 and 8a1, respectively) and through amide nitrogen (6a2) and nitroso oxygen

(8a2).

N N N N N O N N N N N N N O V V V V N N N N O N N O N N 6a 6a 8a 8a 1 2 N 1 2 N N N

Both coordination modes of such ligands give very similar values of the calculated Aiso constant (see for Aiso(scal) in the Table 6). However, the real mode can be found based comparison of their energetic stability. From data obtained, it is evident that dca ligand prefers the bonding via cyano nitrogen (6a1), while the dcnm ligand bonding via nitroso oxygen (8a2).

c) Interaction with bidentate ligands

When vanadocene fragment interacts with bidentate ligands (e. g., dicarboxylic acids) two types of complexes can be formed: (i) chelate complex of single dicarboxylic acid with

18 vanadocene fragment (structures 12a1, 13a1 and 231) or (ii) complex of vanadocene fragment with two molecules of dicarboxylic acid with monodentate bonds (structures 12a2, 13a2 and

232).

O O A COOH O O V A V 12a A = O O 13a A = CH2 A COOH 23 A = CH CH O O 2 2 12a , 13a , 23 12a , 13a , 23 1 1 1 2 2 2 Calculated HFC tensors for both types of complexes together with experimental data are summarised in Table 7. Aiso(scal) obtained for chelate structures 12a1 and 13a1 are in good agreement with experimental Aiso constants. In addition, calculated anisotropic parameters of these complexes are in significantly better agreement with experimental parameters than those calculated for complexes 12a2 and 13a2. Therefore, it can be concluded that complex of vanadocene with oxalic and malonic acids forms a chelate compound. This is in agreement with the results of X-ray diffraction analysis performed for complex 12a. With the increasing size of dicarboxylic acid the difference between Aiso parameters of complexes with chelate and monodentate bonds becomes smaller. The structure of complex 23 cannot be assigned based on Aiso parameters calculated for two possible complex types (see Table 7). However, two structural types can be distinguished based on the differences in anisotropic components of HFC tensor.

Table 7 Calculated and experimental HFC tensors (in MHz) for the vanadocene complexes of dicarboxylic acids.

2 Aiso(calc) Aiso(scal) Aiso(exp) Tx Ty Tz 〈S 〉 12a1 calc. -151.8 -195.2 -- -55.8 -102.8 158.6 0.7800 12a2 calc. -172.7 -219.0 -- -3.1 -141.2 144.3 0.7831 12a exp. -- -- -189.8 -52.0 -117.3 169.4 -- 13a1 calc. -166.2 -211.6 -- -50.8 -109.9 160.7 0.7790 13a1 calc. -172.3 -218.5 -- 1.4 -145.4 144.0 0.7821 13a exp. -- -- -208.1 -47.0 -126.0 173.0 -- 231 calc. -172.8 -219.1 -- -40.3 -117.5 157.8 0.7821 232 calc. -172.3 -218.5 -- 1.4 -145.4 144.0 0.7821

19 2.5 Super-hyperfine coupling tensor

EPR signal of the paramagnetic compounds can be split by magnetic active nuclei of the ligands. This effect, super-hyperfine coupling (S-HFC), is very important effect for structure investigation of the paramagnetic compounds. The S-HFC tensor was calculated for three vanadocene complexes (24, 25 and 26), for 31 1 which was previously observed the strong coupling with P (I = /2, 100%) [21, 22].

Ph + + + Ph O Et S Et P S Me V P V P V S S Me O Et Et 24 25 26

The calculations of the aiso constant were performed using B3PW91 functional and DZP/DZ/DZ basis set (Table 8). The optimised geometries (UB3PW91/DZP/DZ) were used for these calculations.

31 Table 8 Calculated and experimental values of the aiso( P) (in MHz).

a (calc) a (calc) iso iso 〈S2〉 a a (exp) UB3PW91 ROB3PW91 iso 24 152.9 111.3 0.7968 122.9 25 90.0 66.7 0.7981 83.9 26 -109.2 13.7 0.7807 -65.4

a 〈S2〉 value for UB3PW91 calculation.

Complexes with four membered chelate rings 24 and 25 have the magnetic active nuclei, which cause S-HFC, at the twofold axis. The non-bonded distances V–P for complexes 24 and 25 were found 3.14 and 3.20 Å. respectively. Structure of complex 26 is different. The S- HFC is caused by nucleus that is with the donor atom of the ligand that is coordinated to the vanadocene moiety. The bond distance V–P is 2.60 Å.

DFT calculations show that the SOMO orbital contribution to the aiso value is negligible. This parameter is given mainly by spin polarized core orbitals. This conclusion is further supported results obtained at the restricted open-shell level (ROB3PW91) that neglect the spin polarization effect. Different situation was found for complexes 24 and 25. The high values obtained at

ROB3PW91 level show that large contribution of the SOMO orbital. Hence, the aiso constant is given by contribution of both SOMO and spin polarized core orbitals.

20 31 The calculated values of the |aiso( P)| are largely overestimated (0 - 71%). Thus, such calculations cannot be used for estimation of the exact value of the aiso constant. DFT gives only for qualitative description of the S-HFC. They can be used for the prediction of the appearance S-HFC in the EPR spectra of vanadocene complexes.

2.5.1 Using of S-HFC calculations for structure investigation

a) The proving of the bonding mode for phosphate and carbonate ligands

O O OH P C OH O O O OH O O V P V V C O V O O OH O O OH P OH C OH 271 272 281 282 O O

Based on DFT calculations, it is possible to predict the appearance of the S-HFC in the EPR spectrum. Such method was used for structure proving of the complexes that are formed by reaction of the vanadocene dichloride (1a) with phosphates and carbonates. Two structure types were proposed for interaction with these ligands: i) chelate structures (271 and 281) ii) structures with monodentate bonded ligand (272 a 282). The calculations show that only 31 13 chelate complexes 271 and 281 can split EPR signal by nuclei of the ligands ( P, C). The previously made calculations indicate that calculated aiso is largely overestimated. In the case of the carbonate complex 281 the S-HFC should be at the detection limit of the EPR spectroscopy.

Table 9 Comparison of calculated value of the aiso constants (in MHz) with experiments.

a(calc) a (calc) iso iso 〈S2〉 a a (exp) UB3PW91 ROB3PW91 iso 271 calc. 142.4 118.4 0.7800 -- 272 calc. 12.3 13.3 0.7872 -- 27 exp. ------81.5 281 calc. 37.5 28.2 0.7791 -- 282 calc. 4.4 4.6 0.7838 -- 28 exp. ------24.1

a 〈S2〉 value for UB3PW91 calculation.

Phosphate complex 27 was prepared by reaction of the complex 1a with Na2HPO4. The 13 1 reaction of 1a with sodium carbonate labeled by C (I = /2, 99%) was used for preparation of

21 the complex 28. Both complexes give the EPR spectra with super-hyperfine coupling on doublet 1:1 (see Figs. 8 and 9). The S-HFC of complexes 27 and 28 is caused by nucleus 31P 1 13 1 (I = /2, 100%) and C (I = /2, 99%), respectively. The complex 28 gives weak S-HFC (|aiso| = 24.1 MHz). This one is distinct at the first line of the spectrum and its derivation (Fig. 10).

Fig. 8 EPR spectrum of the complex 27 (ν = 9.451 GHz).

Fig. 9 EPR spectrum of the complex 28 with carbonate ligand labeled by 13C (ν = 9.453 GHz).

a) b) Fig. 10 EPR spectrum of the complex 28 with carbonate ligand labeled by 13C (ν = 9.453 GHz). a) The first line of the EPR spectrum. b) Second derivation of the absorption band.

22 b) The proving of the structure for the cyanide complex 5a

CN V CN

5a The structure of the complex 5a was proposed based on spectroscopic measurements. The substitution of the chloride ligands with cyanides was proved by infrared and Raman spectroscopy. Such substitution was accompanied with large changes of EPR parameters

(Aiso, giso). The performed DFT calculations show that complex 5a should give strong S-HFC 13 by nuclei of C of the cyanide ligands (aiso(UB3PW91) = -50.6 MHz). This expectation was experimentally proved. The figures 11 and 12 show the EPR spectra of the complexes that were prepared by reaction of the vanadocene dichloride (1a) with K12CN a K13CN, respectively. Complex 13 13 Cp2V( CN)2 gives strong S-HFC (1:2:1) that is caused by two equivalent nuclei of C

(aiso(exp) = -44.7 MHz). Such experiment unambiguously proves the substitution of both chlorides by cyanide ligands.

12 Fig. 11 EPR spectrum of the complex Cp2V( CN)2 (ν = 9.453 GHz).

13 Fig. 12 EPR spectrum of the complex Cp2V( CN)2 (ν = 9.453 GHz).

23 3. Conclusions

Based on results, which are discussed in this work, EPR spectroscopy is very useful method for structure investigation of the paramagnetic vanadocene compounds. Especially, the HFC tensor gives important information about the coordination sphere of the central metal. Preparation of 23 new vanadocene complexes is described in this work. The X-ray structure analysis was done for 10 complexes. Experimental EPR spectroscopic data were obtained for all prepared complexes. Hyperfine coupling of vanadocene complexes was studied by DFT methods. The very good agreement was found for Aiso constant that was calculated using B3PW91 functional ~ (DZP/DZ basis set) and scaling using equation 1. The anisotropic part ( T ) is in good agreement with experiment (without scaling). It was shown that experimental obtained HFC tensors together with DFT calculations could conclude about the proposed complex structure. Super-hyperfine coupling (S-HFC) is further important effect that gives important information about the complex structure. Appearance of the S-HFC was predicted and subsequently experimentally proved for some vanadocene compounds. Experimental and theoretically obtained data proved that substitution of the acido-ligands largely influence the HFC tensor of the vanadocene compounds. The largest changes in Aiso constant were found for reaction, in which the donor atom of the acido-ligand is changed or chelate ring appears. The S-HFC was observed only for compounds, in which the magnetic active nucleus is bonded to the central metal (compound 5a), and for compounds wit four membered chelate ring (compounds 27 a 28).

References [1] P. Köpf-Maier, H. Köpf, Chem. Rev. 1987, 87, 1137-1152. [2] O. J. D'Cruz, P. Ghosh, F. M. Uckun, Biol. Reprod. 1998, 58, 1515-1526. [3] G. L. Karapinka, W. L. Carrick, J. Polym. Sci. 1961, 55, 145. [4] H. Sinn, W. Kaminsky, H. J. Vollmer, R. Woldt, Angew. Chem.-Int. Edit. Engl. 1980, 19, 390. [5] P. Köpf-Maier, H. Köpf, Struct. Bonding 1988, 103. [6] W. Kaminsky, M. Arndt, Adv. Polym. Sci. 1997, 127, 143.

24 [7] M. Pavlišta, R. Bína, Z. Černošek, M. Erben, J. Vinklárek, I. Pavlík, Appl. Organomet. Chem. 2005, 19, 90-93. [8] M. Munzarová, M. Kaupp, J. Phys. Chem. A 1999, 103, 9966-9983. [9] O. L. Malkina, J. Vaara, B. Schimmelpfennig, M. Munzarová, V. G. Malkin, M. Kaupp, J. Am. Chem. Soc. 2000, 122, 9206-9218. [10] M. L. Munzarová, P. Kubáček, M. Kaupp, J. Am. Chem. Soc. 2000, 122, 11900- 11913. [11] M. L. Munzarová, M. Kaupp, J. Phys. Chem. B 2001, 105, 12644-12652. [12] A. C. Saladino, S. C. Larsen, J. Phys. Chem. A 2003, 107, 1872-1878. [13] N. Tzavellas, N. Klouras, C. P. Raptopoulou, Z. Anorg. Allg. Chem. 1996, 622, 898- 902. [14] P. Ghosh, S. Ghosh, C. Navara, R. K. Narla, A. Benyumov, F. M. Uckun, J. Inorg. Biochem. 2001, 84, 241-253. [15] P. Ghosh, A. T. Kotchevar, D. D. DuMez, S. Ghosh, J. Peiterson, F. M. Uckun, Inorg. Chem. 1999, 38, 3730-3737. [16] J. Holubová, Z. Černošek, I. Pavlík, Collect. Czech. Chem. Commun. 1996, 61, 1767- 1772. [17] M. Morán, Transit. Met. Chem. 1981, 6, 42-44. [18] A. T. Casey, J. B. Raynor, J. Chem. Soc.-Dalton Trans. 1983, 2057-2062. [19] G. Doyle, S. Tobias, Inorg. Chem. 1968, 7, 2479-2484. [20] J. Vinklárek, H. Paláčková, J. Honzíček, Collect. Czech. Chem. Commun. 2004, 69, 811-821. [21] M. Morán, I. Cuadrado, J. Organomet. Chem. 1986, 311, 333-338. [22] R. Choukroun, B. Douziech, C. Pan, F. Dahan, P. Cassoux, Organometallics 1995, 14, 4471-4473.

Abbreviations used in text

~ A - hyperfine coupling tensor

Aiso - isotropic hyperfine coupling constant acac - acetylacetonate bpy - 2,2'-bipyridine 5 Cp - cyclopentadienyl, η -C5H5

25 5 Cp' - methylcyclopentadienyl, η -CH3C5H4 Cg - centroid of the Cp ring dca - dicyanamide dcnm - dicyanonitrosomethanide DFT - Density Functional Theory EPR - Electron Paramagnetic Resonance ~g - g-tenzor

giso - isotropic g-factor HFC - hyperfine coupling hfpd - hexafluorpentadionate I - nuclear spin IR - Infrared Spectroscopy Me - methyl phen - 1,10-phenathroline i-Pr - isopropyl RO - "restricted open shell" 〈S2〉 - the squared value of the total electronic spin ~ T - anisotropic part of the HFC tensor tcm - tricyanomethanide trop - 2-hydroxy-2,4,6-cyclohexatriene-1-onate S-HFC - super-hyperfine coupling U - "unrestricted"

Papers Published by Author:

1. J. Honzíček, P. Nachtigall, I. Císařová J. Vinklárek, Synthesis, characterization and structural investigation of the first vanadocene(IV) carboxylic acid complexes prepared from the antitumor agent vanadocene dichloride, J. Organomet. Chem. 2004, 689, 1180- 1187. 2. J. Vinklárek, H. Paláčková, J. Honzíček, Experimental and theoretical study of the first vanadocene(IV) complexes of α-amino acid prepared from the antitumor agent vanadocene dichloride, Collet. Czech. Chem. Commun. 2004, 69, 811-821.

26 3. J. Honzíček, J. Vinklárek, M. Erben, I.Císařová, µ2-Oxo-bis[azido-bis(η5- cyclopentadienyl)-titanium(IV)], Acta Cryst. 2004, E60, m1090-1091. 4. J. Vinklárek, J. Honzíček, J. Holubová, Interaction of the antitumor agent vanadocene dichloride with phosphate buffered saline, Inorg. Chim. Acta 2004, 357, 3765-3769. 5. J. Vinklárek, J. Honzíček, J. Holubová, An experimental and theoretical study of the 13 Cp2VO2CO: the first observation of C super-hyperfine coupling of metallocene complexes, Magn. Reson. Chem. 2004, 42, 870-874. 6. J. Honzíček, J. Vinklárek, P. Nachtigall, A density functional study of EPR hyperfine coupling for vanadocene (IV) complexes, Chem. Phys. 2004, 305, 291-298. 7. J. Honzíček, J. Vinklárek, M. Erben, I. Císařová, Bis(η5cyclopentadienyl)-bis(N- thiocyanato)-vanadium(IV), Acta Cryst. 2004, E60, m1617-1618. 8. J. Honzíček, I. Císařová and J. Vinklárek Acetonitrile-chloro-bis(η5-cyclopentadienyl)- vanadium(IV) tetrachloro-iron(III), Acta Cryst. 2005, E61, m149-151. 9. J. Honzíček, M. Erben, I. Císařová, J. Vinklárek, Synthesis Characterization and Structure of Metallocene Dicyanoamide Complexes, Inorg. Chim. Acta 2005, 358, 814- 819. 10. J. Vinklárek, J. Honzíček, J. Holubová, Inclusion compounds of cytostatic active

(C5H5)2VCl2 and (CH3C5H4)2VCl2 with α-, β-and γ- cyclodextrines: Synthesis, EPR study and Investigation of the Antimicrobial Behavior toward Escherichia coli., Centr. Eur. J. Chem. 2005, 3, 72-81. 11. J. Vinklárek, J. Honzíček, I. Císařová, M. Pavlišta, J. Holubová, Synthesis, Characterization and Structure of the Bis(methyl-cyclopentadienyl)vanadium(IV) Carboxylates, Centr. Eur. J. Chem. 2005, 3, 157-168. 12. J. Honzíček, M. Erben, I. Císařová, J. Vinklárek, Bis(η5-methyl-cyclopentadienyl)- bis(cyanato)-vanadium(IV), Appl. Organomet. Chem. 2005, 19, 100-101. 13. J. Honzíček, M. Erben, I. Císařová, J. Vinklárek, Bis(η5-cyclopentadienyl)-bis(azido)- vanadium(IV), Appl. Organomet. Chem. 2005, 19, 102-103. 14. J. Honzíček, I. Císařová, J. Vinklárek, Bis(3-methyl-2-cyclopenten-1-one)dichloro- oxovanadium(IV), Appl. Organomet. Chem. 2005, 19, 692-693. 15. J. Honzíček, H. Paláčková, I. Císařová, J. Vinklárek, Ansa-vanadocene complexes with short interannular bridge, J. Organomet. Chem. 2005 (accepted).

27 16. J. Vinklárek, H. Paláčková, J. Honzíček, M. Holčapek, I. Císařová, Investigation of vanadocene(IV) α-amino acids complexes, Synthesis, structure and behavior in physiological solutions, human plasma and blood, Inorg. Chem. 2005 (submitted).

Conferences (International) Lectures:

1. J. Honzíček, J. Vinklárek and P. Nachtigall, An EPR Study of Bis(cyclopentadienyl)vanadium Carboxylates, 19th International Conference on Coordination and Bioinorganic Chemistry, Smolenice, Slovakia, 2.-6.6.2003. 2. J.Honzíček, J.Vinklárek and P. Nachtigall, A Structural Study of Bis(cyclopentadienyl)vanadium Carboxylates, 8th Seminar of PhD Students on Organometallic Chemistry, Hrubá Skála, Czech Republic, September 29.9-3.10.2003. 3. J. Honzíček, M. Erben, P. Nachtigall and J. Vinklárek, Vanadocene(IV) Pseudohalide Complexes: Structural study, 4th International Symposium on Chemistry and Biological Chemistry of Vanadium, Szeged, Hungary, 3.-5.9.2004. 4. J. Honzíček, J. Vinklárek and P. Nachtigall, A theoretical and experimental study of EPR hyperfine coupling of vanadocene(IV) conplexes, 9th Regional Seminar of PhD- Students on Organometallic and Organophosphorous Chemistry, Szklarska Poręba, Poland, 10-14.4. 2005. 5. J. Honzíček, P. Nachtigall and J. Vinklárek, Hyperfine and Super-hyperfine Coupling of Vanadocene(IV) Complexes, 20th International Conference on Coordination and Bioinorganic Chemistry, Smolenice, Slovakia, 5.-10.6.2005.

Posters:

1. J. Vinklárek, M. Erben, A. Růžička, R. Jambor, J. Honzíček: Study of Electonic Structure Titanocene Dihalides, XII FECHEM Conference on Organometallic Chemistry, Gdaňsk, Poland, 2.-7.9.2001. 2. J. Honzíček, J. Vinklárek, J. Holubová and P. Nachtigall, A Study of Interaction of Vanadocene Fragment with Proteins on the Model Systems, 19th International Conference on Coordination and Bioinorganic Chemistry, Smolenice, Slovakia, 2.- 6.6.2003.

28 3. J. Honzíček, J. Vinklárek, P. Nachtigall, EPR Hyperfine Coupling of Vanadocene(IV) Compounds: Theoretical Study, 4th International Symposium on Chemistry and Biological Chemistry of Vanadium, Szeged, Hungary, 3.-5.9.2004. 4. J. Honzíček, H. Paláčková, J. Holubová, I. Císařová, J. Vinklárek, Synthesis and Characterization of Vanadocene(IV) Amino Acid Complexes, 4th International Symposium on Chemistry and Biological Chemistry of Vanadium, Szeged, Hungary, 3.- 5.9.2004. 5. J. Holubová, J. Vinklárek, J. Honzíček, Inclusion Compounds of Vanadocene Dichloride and Cyclodextrines: an ESR Study, Solid State Chemistry 2004, Prague, Czech Republic, 12.-17.9.2004.

Conferences (National) Lectures:

1. J. Honzíček, J. Vinklárek and P. Nachtigall, The interaction of cytostatic active vanadocene dichloride with bioligands, 55th Congress of the Chemical Societies, Košice, Slovakia, 8.-12.9.2003.

2. J. Vinklárek, J. Honzíček and J. Holubová, A Study of cancerostatic active Cp2VCl2 by EPR spectroscopy, 55th Congress of the Chemical Societies, Košice, Slovakia, 8.- 12.9.2003. 3. J.Honzíček, J.Vinklárek, P. Nachtigall and I.Císařová, A study of the pseudohalide

complexes of the type Cp2VX2, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004. 4. H. Paláčková, J. Vinklárek, J. Honzíček, J. Holubová, A study of derivatives of vanadocene dichloride and their effect on the cell division, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004.

Posters:

1. J. Honziček, J. Vinklárek, M. Erben and P. Nachtigall, Assignment of the UV-VIS 0 spectra of d complexes Cp2TiX2 (X = F, Cl, Br, I) using the density functional methods. 54th Congress of the Chemical Societies, Brno, Czech Republic, 30.6.-4.7.2002.

29 2. J. Vinklárek, J. Honziček and P. Nachtigal, Theoretical study of the bonding of d0

complexes Cp2TiX2 (X = F, Cl, Br, I), 54th Congress of the Chemical Societies, Brno, Czech Republic, 30.6.-4.7.2002. 3. J. Honziček, J. Vinklárek, J. Holubová: A study of the derivatives of titanocene dichloride and vanadocene dichloride with anticancer effect, 54th Congress of the Chemical Societies, Brno, Czech Republic, 30.6.-4.7.2002. 4. H. Paláčková, J.Vinklárek and J.Honzíček, A Study of Interaction of Vanadocene Fragment with Proteins on the Model Systems, 55th Congress of the Chemical Societies, Košice, Slovakia, 8.-12.9.2003. 5. J. Honzíček, J. Vinklárek and I. Císařová, An EPR study of Bis(cyclopentadienyl)vanadium Carboxylates, 55th Congress of the Chemical Societies, Košice, Slovakia, 8.-12.9.2003. 6. H. Paláčková, J. Zemanová, J. Vinklárek and J. Honzíček, A Study of inclusive

compounds of the cytostatic active Cp2'VCl2 with cyclodextrines by EPR spectroscopy, 55th Congress of the Chemical Societies, Košice, Slovakia, 8.-12.9.2003. 7. J. Honzíček, J. Vinklárek and J. Holubová, Hydrolysis of vanadocene dichloride and interaction with carbonates, 55th Congress of the Chemical Societies, Košice, Slovakia, 8.-12.9.2003. 8. J. Vinklárek, J. Honzíček and J. Holubová, Interaction of vanadocene fragment with the components of PBS solution that is used for preclinical tests, 55th Congress of the Chemical Societies, Košice, Slovakia, 8.-12.9.2003. 9. J. Vinklárek, J. Honzíček, M. Erben, I. Pavlík, Ligand Field Theory and d-d Spectra of Bent d1 metalocenes, 55.zjazd chemických společností, 8.-12.9.2003, Košice, Slovakia. 10. J. Vinklárek, J. Honzíček, I. Císařová and J. Holubová, Synthesis, Characterization and Structure of the Bis(methyl-cyclopentadienyl)vanadium(IV) Carboxylates, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004. 11. J. Vinklárek, H. Paláčková, J. Honzíček and P. Svobodová, A study of the derivatives of vanadocene dichloride with amino acids with sulphur in side-chain. 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004. 12. J. Honzíček, M. Erben, P. Nachtigall and J. Vinklárek, Vanadocene(IV) pseudohalide complexes, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.- 9.9.2004.

30 13. J. Honzíček, J. Vinklárek, P. Nachtigall, A theoretical study of EPR hyperfine coupling of vanadocene(IV) compounds, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004. 14. J. Vinklárek, J. Honzíček, P. Nachtigall and Z. Černošek, An experimental study of antitumor active vanadocene(IV) complexes, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004. 15. J. Honzíček, J. Vinklárek, M. Svitač and B. Frumarová, Synthesis and characterization of ansa-vanadocene(IV) compounds, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004. 16. H. Paláčková, J. Honzíček, J. Vinklárek and B. Frumarová, Synthesis and characterization of vanadocene complexes of a-amino acids, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004. 17. H. Paláčková, J. Vinklárek and J. Honzíček, Biological activity of complexes of the type

[Cp2V(aa)]Cl on Escherichia coli, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004. 18. M. Erben, J. Vinklárek, I. Císařová and J. Honzíček, Synthesis and structures of µ-oxo titanocene compounds with pseudohalide ligands, 56th Congress of the Chemical Societies, Ostrava, Czech Republic, 6.-9.9.2004.