Binding of Cations to 4f Metal Ions : Preparation and Properties of (III) Complexes Containing the Phenelzinium(l+) Cation as a Ligand Nickolia Lalioti3, John M. Tsangaris*3, Th. F. Zafiropoulos*b, Spyros P. Perlepes*b a Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece b Department of Chemistry, University of Patras, 26500 Patra, Greece Z. Naturforsch. 51b, 112-118 (1996); received May 19, 1995 Lanthanide(III) Complexes, Phenelzine Dihydrogen Sulfate, Cationic Ligands, IR Spectra Treatment of Ln2(S 04)3 • nH20 (Ln = La, Ce, Pr, Nd, Sm. Eu, Gd ; n - 8, 9) with phenelzine dihydrogen sulfate, (phzH2)S 04, in 1 N H2S 0 4 yields polymeric complexes with the general formula [Ln(S04)2(H20 )2(phzH)], which contain the phzH+ cation as a ligand. The compounds have been characterized by elemental analyses, X-ray powder patterns, thermal methods, magnetic susceptibilities and spectroscopic (IR, Raman, electronic diffuse reflec­ tance and solid-state emission f-f spectra) studies. The prepared complexes most probably consist of 7-coordinated units, formed by four bridging bidentate sulfato groups, two terminal aqua molecules and one cationic phzH+ ligand.

1. Introduction We have long been intrigued by the ability of The lanthanide(III) ions were long considered the monoprotonated hydrazininum cation, N2H5+, to be a group of elements with rather simple and to coordinate to Ln(III) ions [18] as an example uninteresting chemistry [1]. More recently, how­ for coordination of positively-charged ligands [19]*. ever, there are applications in a broad variety of This paper concentrates on the preparation and chemical, biological, geological and environmental characterization of neutral, polymeric Ln(III) systems [1, 2], Today, the development of lanthan­ complexes containing the phenelzinium(l+) cat­ ide chemistry is a central theme in inorganic chem­ ion, C6H5CH2CH2NH2NH2 (phzH+), as a ligand. istry, research in this area ranging from bio­ This cation has been shown to coordinate to a vari­ inorganic fields [3, 4] to catalysis [5] and materials ety of transition metal ions [20]. science [6, 7]. 2. Experimental During the last several years, we have been in­ volved in developing certain aspects of the coordi­ All synthetic operations were performed under nation chemistry of 4f metal ions with oxygen and/ aerobic conditions. The salts Ln2(S04)3-nH20 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd; n = 8, 9) were or nitrogen ligation, employing neutral or anionic obtained from Aldrich and Alfa. Phenelzine di­ ligands [8-17]. Extension of our work on Schiff hydrogen sulfate, (phzH2)S04, was synthesized as base ligands [14] revealed that groups with poor described earlier [20, 21]; its purity was checked donor strength, i.e. carbonyl ester oxygens, can co­ by microanalyses. Warning: (phzH2)S04 is a skin ordinate to 4f ions. More recently [17], we have irritant; rubber gloves are essential for its hand­ employed both CF^CC^- and 1,10-phenanthroli- ling. The solvents and chemicals used were of ne(phen) as ligands and have prepared the qua- reagent grade, without further purification. The druply-bridged, antiferromagnetically-coupled di- metal content was determined by with nuclear complexes [Ln2(CFl3C02)6(phen)2] (Ln = ethylenediaminetetraacetate using Xylenol Or­ Ce, Pr, Eu, Gd, Dy) ; EPR studies of these com­ ange as indicator. Microanalyses for C, H and N were performed at the Microanalytical Labora­ pounds have shown intramolecular magnetic in­ tory, University of Liverpool, U. K. Physicochemi­ teraction between two 4f ions. cal measurements and spectroscopic techniques were carried out by published methods [22-24],

* Reprint requests to Prof. Dr. J. M. Tsangaris, Prof. Dr. Th. F. Zafiropoulos or Dr. S. P. Perlepes.

0932-0776/96/0100-0112 $06.00 © 1996 Verlag der Zeitschrift für Naturforschung. All rights reserved. D N. Lalioti et al. ■ Binding of Cations to 4f Metal Ions 113

Preparation of the metal complexes The lanthanide(III) complexes of the present The complexes [Ln(S04)2(H20 )2(phzH)]v were work were prepared as summarized in eq. (1): all prepared similarly. A hot, filtered, solution of Ln2(S 0 4)3 A7H20 (4.0 mmol) in IN H2S 0 4 was 2x(phzH2)S04 + 1 xLn2(S04)3 nH20 ~ (^=SC>4> treated with 8.0 mmol of (phzH2)S04. The ob­ tained solution was stirred at 50-60 °C for 30 min. 2 [L n(S04)2(H 20 ) 2(phzH )]t + 1x H,S0 4 + ( /i- 4 ) x H ,0 The flask was stored overnight at room temper­ (1) ature and the resultant microcrystalline material Ln = La, Ce, Pr, Nd, Sm, Eu, Gd; n = 8 or 9; was collected by , washed with H20, (phzH2)S04 - (C6H5CH2CH2NH2NH3)S04; EtOH and Et20, and dried in vacuo over P4O 10. Similar reactions with 4.0 mmol of phzH+ = C6H5CH2CH2NH2NH2 Ln2(S04)3 nH20 and 16.0 mmol of (phzH2)S04 also gave the same complexes, as did stirring the The phzH+ ions are produced from the dissoci­ reaction solutions for a few hours. ation of phzH22+ ions; it is known [34] that N2H62+ Efforts to prepare analogous compounds of ions dissociate in water, even in slightly acidic so­ heavier were not successful due to lutions [18], to give N2H5+ and H 30 + ions. contamination of the products with starting metal Lanthanide(III) ions, being typical “hard acids” sulfates (analytical and IR evidence). This paral­ in the HSAB sense, generally have a low affinity lels the behaviour observed for the lanthanide(III) toward nitrogen donor atoms. Therefore, the pres­ complexes of N2H5+ [18]. ence of coordinated phzH+ ions in complexes pre­ pared from aqueous solution is rather unusual. It seems that the neutral [Ln(S04)2(H20 )2(phzH)]v species is the thermodynamically preferred pro­ 3. Results and Discussion duct in the Ln(III)/phzH22+/l N H2S04 reaction Hydrazine and substituted hydrazines, like system. phenelzine (phz), offer the possibility of several Colours, yields, analytical data and effective different types of coordination behaviour toward magnetic moments are given in Table I. The iso­ metal ions. In their neutral form, they can function lated complexes are microcrystalline or powder- as monodentate ligands, but may also serve as like, stable in atmospheric conditions, and have a bridging bidentate ligands [25, 26]. Hydrazines are moderate solubility in DMF and DMSO. We had also found as hydrazido(l-) and hydrazido(2-) hoped to structurally characterize one of the com­ ligands, representative examples from lantha- plexes by X-ray crystallography (working mainly nide(III) chemistry being the complexes with DMF), but were thwarted by twinning prob­ (C5Me5)2Sm(n2-PhNHNPh)(THF) and lems or lack of single crystals. Thus, the character­ [(C5Me5)2Sm]2(//-«2:A72-HNNH), respectively [27]. ization of the complexes is based on other physical It is worth mentioning that the discovery of the techniques and on spectroscopic methods. dinitrogen reduction with (C5Me5)2Sm, to yield Dilute solutions of the complexes in MeNO? the trivalent complex [(C5Me5Sm] 2(«-«2:/i2-N2), (non-donor solvent) are non-conducting, support­ has opened up new opportunities to use lantha­ ing the view that these are non ionic species. X-ray nide metal complexes to derivatize substrates powder diffraction patterns in the 4° < 2 6 < 50° containing NN linkages [28]. The monoprotonated range indicate that each solid represents a definite hydrazinium cations can retain a basic site and compound, which is not contaminated with start­ should also be capable of coordination. The only ing materials or/and byproducts. The data also adequately characterized complexes containing co­ indicate that the prepared complexes are ordinated hydrazinium ions are [MII(S 0 4)2(N2H5)2].x: isostructural. (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd) [29-31], The thermal decomposition of the complexes [Cu1ICl3(N2H5)], [32], [CuI2Cu1ICl6(N2H5)2] [33] was studied using TG/DTG, DTA and DSC tech­ and [Ln,n(S04)2(H20)(N2H5)L (Ln = La, Ce, Pr, niques under nitrogen. We first comment on the Nd, Sm) [18]. Hydrazines are potent reducing dehydration process. The TG/DTG and DTA agents in aqueous solution, so that various redox curves of complexes 2-6 show a first, one-step (as reactions are also possible [32, 33], revealed from the appearance of only one DTG 114 N. Lalioti et eil. • Binding of Cations to 4f Metal Ions

Table I. Colours, yields, analytical resultsa and effective magnetic moments of the complexes.

No.Compound Colour Yield (% )b [%] Ln C H N ^eff(B M )c

1 [La(S04)2(H20 )2(phzH)]v white 63 Calcd 27.54 19.05 3.40 5.56 dia Found 27.51 19.33 3.32 5.33 2 [Ce(S04)2(H20 )2(phzH)]A off white 67 Calcd 27.72 19.01 3.40 5.54 2.43 Found 27.43 18.77 3.51 5.27 3 [Pr(S04)2(H20)2(phzH)]v pale green 61 Calcd 27.83 18.98 3.39 5.53 3.48 Found 28.40 19.36 3.23 5.55 4 [Nd(S04)2(H20)2(phzH)]v pale lilac 68 Calcd 28.30 18.85 3.37 5.50 3.56 Found 27.99 18.41 3.60 5.41 5 [Sm(S04)2(H20)2(phzH)], cream 70 Calcd 29.15 18.63 3.33 5.43 1.58 Found 28.30 19.00 3.57 5.16 6 [Eu(S04)2(H20 )2(phzH)]v white 70 Calcd 29.37 18.57 3.32 5.42 3.39 Found 29.80 18.63 3.20 5.20 7 [Gd(S04)2(H20 )2(phzH)]v white 75 Calcd 30.09 18.38 3.28 5.36 7.92 Found 30.87 18.60 3.40 4.99

11 The H20 content was also confirmed by TG/DTG analysis; b based on the metal; c per lanthanide(III) ion at room temperature; phzH + = C6HsCH2CH2NH2NH2; dia = diamagnetic. maximum) endothermic mass loss at 250-295 °C, dehydration for reaction (2). The AH value which corresponds to the release of the entire was found to be 107.0 kJ mol-1; this value is water content. The high temperature of H20 loss high enough to suggest that coordinated water is indicates that the two water molecules are coordi­ removed [11, 12. 36]. The thermal stability se­ nated to the metal ions; this is also confirmed by quence of [Ln(S04)2(H20 )2(phzH)]v - as indi­ IR (see below). Clear plateaux are cated by the temperature of initial weight loss - not reached after the complete dehydration of is La < Ce < Pr < Nd < Sm < Eu < Gd; a systematic 2-6, because the decomposition of the anhydrous increase in thermal stability with decreasing lan­ species starts immediately. Complex 1 releases the thanide ion size is clearly evident indicating water molecules endothermically in two distinct stronger Ln-O H2 bonds. steps. The TG/DTG curves show a first mass loss The dehydrated compounds decompose with between 245 and 263 °C, corresponding exactly to rather simple degradation mechanisms and with­ the release of one water molecule per La(III). A out formation of thermally stable intermediates. small plateau is reached at about 267 °C. There is a The decomposition residues at ca. 500 °C appear second, sharp distinct inflection in the 280-295 °C to be Ln2(S04)3 (IR evidence). region; again a clear plateau is not reached after The room-temperature effective magnetic mo­ the removal of the second water molecule. The ments of the paramagnetic complexes 2 -7 show activation E„ of the dehydration reaction little deviation from Van Vleck values [37] indicat­ 94S-263 °C ing thereby that the 4 f electrons do not participate [La(S04)2(H20 )2(phzH)]v -----—------> IN 2 much in bonding [38]; these electrons are well shielded by the (5s)2(5p)6 octet. [La(S04)2(H20)(phzH)].v + .tH20 T (2) The solid-state electronic spectra (diffuse reflec­ was determined by the variable heating rate tance spectra) of the complexes involve mainly in­ method proposed by Flynn and Wall [35]; full ex­ traligand and f-f transitions. The spectra show a perimental details of this method have also been shift of f-f bands towards lower as com­ given in ref. [24], The average E„ value of 188.9 kJ pared to those of the corresponding aqua ions. mol“1 is characteristic for the removal of co­ This red shift, which is a measure of metal-ligand ordinated water [11-13, 36], By differential scan­ covalent binding, has been ascribed to the nephe- ning (DSC) at a heating rate of 5 °C lauxetic effect upon complexation [39], The values min 1 we have also measured the enthalpy of of the bonding parameters ß(nephelautexic ratio). N. Lalioti et al. • Binding of Cations to 4f Metal Ions 115

Table II. Bonding parameters of the Pr(III), Nd(III) and crystal structure) with the spectrum of 4 in the re­ Sm(III) complexes calculated from the f-f diffuse re­ gion of the above mentioned transition, it is con­ flectance spectra. cluded that Nd in [Nd(S04)2(H20 )2(phzH)]v is £1/2 Compound ß (%) seven-coordinated [44],

3 0.993a + 0.70 0.059 Useful information concerning the nature of the 4 0.992b + 0.81 0.063 chromophore and geometry of lanthanide com­ 5 0.989c + 1.11 0.074 plexes can be obtained by the study of the emis­ sion f-f spectra [1, 45]. Among lanthanide(III) a Calculated from the 3H4 —» lT>2, 3P<), 3Pi and 3P2 transitions; b calculated from the 4I9/2 —»• 4F5/2> 2Hy/2, complexes in which strong emission has been ob­ (4F7/2, 4S3/2), 2H u /2, (4G5/2, 2G7/2), (2K13/2, 4G7/2, 4G9/2), served, Eu(III) complexes have been the subject 2K i5/2, (2G9/2), 2D 3/2, 2P3/2), 4G 11/2 and (2Pi/2, 2D 5/2) tran­ of extensive studies since the low 7 values give rise sitions; c calculated from the 6H5/2 —► 4M15/2, 4Ii3/2, to a smaller number of closely spaced energy (6p 4P)5/2j 6p 3/2and 6P7/2 transitions. levels. Of primary interest are the transition mani­ folds, ',D0 to 7F0, 5D0 to 7Fi, and -“'D q to 7F2, since (3(Sinha’s parameter) and fr1/2(covalent factor) of these transitions are normally intense and may the Pr(III), Nd(III) and Sm(III) complexes give clues as to the site symmetry. Complex 6 (Table II), calculated [40-42] from the solid-state shows strong red luminescence at 77 K under both f-f spectra by eq. (3)-(5), indicate relatively little short-wave UV and dye laser excitations. Band as­ covalent character, i. e. the signments (Table III) and determination of the crystal field site symmetry by the examination of 1 ^complex Eu(III) band splittings were made by n v (3) n = 1 acluo methods described elsewhere [45, 46]. The groups of sharp lines were easily assigned to transitions l-ß %<3 x 100 (4) from the lowest excited "’D level, 5D0, to 7F0_5 levels. Only weak emission from higher levels was observed, indicating efficient multiphonon bm = (l-ß ) (5) deexcitation by high-energy lattice vibration modes. Closer examination of the emission interaction between Ln3+ and the ligands is essen­ spectrum reveals the total lifting of the 7F level tially electrostatic, and that there is a small partici­ degeneracy resulting usually in 27+1 lines for pation of 4f orbitals in bonding [40-43]. each "’D q —► 7Fj transition. The absence of an in­ The shape and fine structure of some hypersen­ version centre in 6 is confirmed by the larger in­ sitivity bands for Nd(III) have been related to co­ tensities of the transitions to the 7 = 2 and 7 = 4 ordination number [44] ; four transitions are sensi­ sublevels, with respect to the intensity of the mag- tive to coordination environment but one, 4I9/2 —► netic-dipole allowed transition to the 7 = 1 sub- 4G5/2, 2G7/2 at about 590 nm, is particularly so. By level [47], The number of the observed lines is in comparing the spectra of standard Nd(III) com­ accordance with the low symmetry Cs of the pounds (complexes with known molecular and Eu(III) site [45, 48]. For Cs symmetry no selection

Table III. Solid-state fluorescence spectraab (nm) of [Eu(S04)2(H20 )2(phzH)]Ji;.

Assignment0 Assignment0

5D() - 7F0 580.5 wm 5D 0 - 7F3 647.5 w, 649.5 sh, 653.0 w, 656.0 w, 5D 0 - 7F] 590.0 m, 591.5 m, 596.0 wb 657.5 sh, 659.0 w 5D„ - 7F2 611.5 s, 613.5 sh, 616.0 vs, 622.5 m, 626 mb 5D„ - 7F4 684.5 w, 688.5 sh, 692.5 m, 695.0 sh, 696.5 m, 698.5 s, 700.5 sh, 702.0 ms

a Obtained at liquid nitrogen temperature; b emission originates almost totaly from the 5D0 excited state (bands associated with 5D! 2 —*• 7F0.i,2 transitions are extremely weak); c the breakdown of the free-ion selection rule AJ = 2, 4 or 6 for electric-dipole transitions caused also weak transitions to 7F5. vs = very strong, s = strong, m = medium, w = weak, b = broad, sh = shoulder. 116 N. Lalioti et al. ■ Binding of Cations to 4f Metal Ions

Table IV. Diagnostic IR bands3 (cm ') of the representative complexes 1, 3, 5 and 6.

Assignments15-0 1 3 5 6

v(OH)coord water 3405 s 3397 s 3389 m 3386 s t'(NH) 3250 s, 3135 mb, 3110 m 3240 s, 3140 mb, 3105 mb 3230 sb, 3130 mb, 3100 m 3235 s, 3125 sb,3105 mb d Ö(OH)COOrd. water 1622 sh 1623 w 1619 sh v(N -N ) 1164 s 1167 m 1166 m 1168 s v3( s o 4 ) 1185 s, 1110 s, 1027 s 1179 s, 1095 s, 1037 s 1182 s, 1100 s. 1045 s 1183 s, 1113 s, 1033 s v ,(S 0 42-) 993 m 990 w 982 w 985 m pr(OH)coord. water 830 m 826 m 823 w 825 m v4(S 0 42-) 641 s, 613 s, 577 m 644 s, 607 s, 583 m 632 s, 609 m, 586 m 637 s, 614 m, 591 m v2(SQ42-) 474 w 470 w 471 w 469 w

a Fourier-transform spectra; b the IR spectrum of (phzH2)S04 exhibits v(NH) at 3639 m, 3418 m and 3308 mb, v (N -N ) at 1177 m, v3(S 0 42-) at 1115 s and v4(S 0 42~) at 608 m cm -1 (the and v2(E) modes of the Td S 0 42- ion are not IR-active and appear as very weak bands at 964 and 425 cm '1); c the IR spectrum of the free base phenelzine (phz) exhibits v(N-H ) at 3300 m, 3104 m and 3082 mb, and v(N-N) at 1125 cm-1; d not observed, v = stretching vibration, <3 = in-plane deformation, £>r = rocking mode.

rules apply and all transitions between crystal field bands in the region 2860 to 1650 cm-1’ the Stark levels are allowed. This site symmetry, to­ [Ln(S04)2(H20 )2(phzH)] complexes show broad gether with the physical and spectral data obtained unresolved absorptions (not listed in Table IV) in for 6, suggest that this complex has the rather rare the 2800- 2400 cm-1 region. These are assigned 7-coordinated trigonal base-tetragonal base (Cs) to strongly hydrogen-bridged N-H stretchings structure [49]. Most lines observed are of pure and indicate that the prepared complexes are electronic origin; no vibronically induced transi­ characterized by strong, probably intermolecular tions could be found. The line widths are about +N -H -"0 hydrogen bonds. It is worth noting 0.4 nm with the exception of two broad bands at at this point that the crystal structure of 596.0 and 626.0 nm. [Nd(S04)2(H20)(N2H5)]Jt is built up of Nd(III) Table IV gives diagnostic IR bands for four (1, atoms linked by sulfato groups forming sheets, 3, 5, 6) representative complexes. Assignments of with the sheets being held together by the characteristic IR bands were given by studying N-H--O(sulfate) type hydrogen bonds [18]. (a) deuterium isotopic substitution shifts, (b) dif­ The N -N stretching frequencies of hydrazines ferences between the spectra of phz, (phzH2)S04 and their salts and complexes generally allow to and the prepared complexes, and (c) literature re­ distinguish the various coordination possibilities ports [18, 20, 31, 32, 50-53], The IR evidence pre­ [20, 32, 52]. In the spectrum of free phenelzine sented below supports the contention that the pre­ (phz) the band at 1125 cm-1 is due to v(N-N) pared compounds are not the double salts [20], The large shift ( ca. 45 cm-1) of this band to (phzH)2S04-Ln2(S04)3-4H20 or anionic com­ higher wavenumbers observed in the spectra of plexes (phzH)[Ln(S04)2(H20 )2], both containing the prepared complexes is characteristic of coordi­ the free phenelzinium(l+) cation, but coordina­ nated hydrazinium cations [18, 20, 32] and more tion compounds in which this cation is bonded to generally of bridged hydrazines [52]; similarly the metals. there is a shift of v(N-N) to higher wavenumbers The IR spectra of the complexes exhibit a me­ in diprotonated phenelzine, i.e. (phzH2)S 0 4 [52], dium to strong intensity band at 3405-3385 cm-1, The distinction between uncoordinated (point assigned to v(OH)coord.water [50, 51] ; its broadness group Td), unidentate (C3v) and bidentate (C2v) and rather low frequency are both indicative of S042- by IR spectroscopy is very straightforward hydrogen bonding. The (3(OH) and £>r(H20) [51], In the spectra of the prepared complexes, modes of the coordinated water appear at ca. 1625 both vx and v2 modes appear with weak to medium and 820 cm-1, respectively [51]. intensity, and v3 and v4 each split into three bands. The spectra of the complexes exhibit three This result suggests a lowering of symmetry from medium to strong, broad v(NH) bands in the Td to C2v; thus, the sulfato groups in 3250-3150 cm-1 region. Whilst phz shows no [Ln(S04)2(H20 )2(phzH)]v are bidentate [51], N. Lalioti et al. • Binding of Cations to 4f Metal Ions 117

Even though bridging and chelating bidentate sul­ fates can not be distinguished on the basis of the number of bands they give, it appears that the v3 frequencies in the former are lower than in the latter [51]; thus, the distinction between bridging and chelating sulfato ligands can be made on this basis. The v3 bands in the spectra of the prepared complexes are in similar positions to those of other bridging bidentate sulfato complexes [51, 53], including those of [Mn(S04)2(N2H5)2]r [31], nh2 s nh2 The IR spectrum of 1 is different from the spectrum of the known [20] double salt \ ' / " ° \ 1 X H20 — Ln H20 — Ln 3(phzH)2S04 • La2(S04)3 • 4 H20 in the v(OH), v(NH), v(N-N) and S042- regions, in agreement 2 OH2 with our proposal that 1 is a complex in which the phzH+ cation is bonded to La(III). I In the far-IR spectra (450-250 cm-1) of the complexes, four bands at ca. 420, 380, 350, and groups, two terminal aqua molecules and one 320 cm-1 appear to reflect the dependence of phzH+ ligand. However, the formation of sheets structure on lanthanide ion radius. These bands cannot be ruled out. Molecular models show that probably contain large contributions from the such structures are quite feasible. A complex hy­ v(Ln-O sulfato), v(Ln-O water) and v(Ln-N) modes drogen bonding scheme involving the hydrogens [11, 13, 14, 18, 54, 55]; however, unambiguous as­ from phzH+, sulfate oxygens and water molecules signments are not possible. A systematic increase certainly contribute to the stabilization of the in the frequency of these vibrations with decreas­ structure. ing metal ion radius is clearly evident, indicating There are two possible formulae for the coordi­ stronger metal-ligand bonds from La(III) to nated phzH+ ion, i.e. C6H5CH2CH2NHNH3 (II) Gd(III). The rather abrupt frequency increase of and C6H5CH2CH2tiH 2NH2 (III); only the dipro- the metal-ligand stretching modes in 7 can be at­ tonated base C6H5CH2CH2NH2I^H3 is known in tributed to the stabilization caused by the half­ salts. We believe that III is the more likely formula filled 4f shell of Gd(III) [56]. for phzH+, as IR studies [58] have shown that in Strong fluorescence made it impossible to re­ alkyl hydrazines protonation occurs on the cord useful Raman spectra for most of the com­ nitrogen bonded to carbon. Thus, in plexes prepared, either with the He-Ne laser or [Ln(S04)2(H20 )2(phzH)]x it seems that the termi­ with various lines of the Ar+ laser ; satisfactory nal nitrogen is bonded to the lanthanide. Such a Raman spectra could only be obtained for 1 and 7. bonding of phzH+ is also expected for steric Tentative assignments [51, 52, 55, 57] of the most reasons. characteristic bands for 1 are as follows: v(N-H) We are currently investigating the reactivity at 3245 w, 3139 m, and 3104 wb, v(N -N ) at 1162 m, chemistry of the above described complexes and v3(S 0 42-) at 1181 s, 1108 s, and 1032 m, v^SC V -) at seeking access to additional Ln(III) species with 997 vs, v4(S 042~) at 643 m, 610 m, and 570 w, other cationic ligands. v2(S 0 42-) at 460 m and 444 m, v(Ln- Osulfato/water) at 424 m, 373 s, and 342 w, and v(L n-N ) at 312 w Ackno w ledgem en ts cm-1. We wish to thank Prof. H. O. Desseyn (Labora­ From the overall physical and spectroscopic torium Anorganische Scheikunde, Rijksuniversi- study presented above, it is concluded that 1 -7 tair Centrum Antwerpen, Belgium) for providing may have the oligomeric or polymeric chain struc­ some instrumental facilities (far-IR, Raman, ther­ ture shown in I, i.e. they consist of the 7-coordi- mal). We also thank A. Panagiotopoulos for his nated [Ln(Osulfato)4(Oaqua)2(NphzH+)] coordination contribution to the initial stages of this work and sphere, formed by four bidentate bridging sulfato NATO for partial financial support. 118 N. Lalioti et al. ■ Binding of Cations to 4f Metal Ions

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