Spectral Investigation of Some Calix N Arene Functionalised at Lower Rim

STUDIA UNIVERSITATIS BABEŞ-BOLYAI, PHYSICA, SPECIAL ISSUE, 2003

SYNTHESIS AND CHARACTERISATION OF SOME NEW CALIX[n]ARENE DERIVATIVES

Traian-Nicolae URSALEŞ 1, Elisabeth-Jeanne POPOVICI1, Ioan SILAGHI- DUMITRESCU2, Nicolae POPOVICI1 and Adina URSALEŞ1

1 "Raluca Ripan" Institute for Research in Chemistry, Fantanele 30, PO Box 702, R- 3400 Cluj-Napoca; e-mail: [email protected] 2 Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, R-3400 Cluj-Napoca, Romania

Abstract The synthesis of new calix[n]arene derivatives was attempted by selective alkylation with dichlorophenylphosphinoxide and 2-butenyl bromide, in the presence of sodium hydride as a base. The results of FT-IR, 1H-NMR and 31P-NMR spectroscopic investigations are in good agreement with the expected structure and purity of such prepared material. Keywords: calixarene, dichlorophenylphosphinoxide, E-2-butenyl bromide, alkylation.

1. Introduction Calix[n]arene are cyclic oligomers of phenol-formaldehyde condensates. This class of compounds has generated a particular interest because of their natural basket-shaped cavities associated with versatile recognition properties towards ions and neutral molecules as well1-3. By selective functionalisation at the OH phenolic groups (lower rim) and/or in the para positions of the phenol ring (upper rim), specific receptors for cations4, anions5 and neutral molecules6 could be prepared. With the purpose to obtain some new calixarenes derivatives with increased ability to extract lanthanide ions, the selective alkylation of p-tertbutyl calix[n]arenes with dichlorophenylphosphinoxide and 2-butenyl bromide was attempted. The paper presents our results referring to the synthesis and characterisation of some new compounds from this class.

2. Experimental part The calixarene derivatives were prepared in the presence of sodium hydride (NaH), by the reaction between calix[4],calix[6],and calix[8]arenes with E- 2-butenyl bromide (crotyl bromide) and dichloro-phenylphosphinoxide, in acetonitril or dimethylformamide- tetrahydrofuran medium. The syntheses were performed at reflux, under inert atmosphere. FT-IR (KBr pellets; JASCO-615 Spectrometer), 1H-NMR (tetramethylsilane; 80MHz Brucker Spectrometer) and 31P-NMR (phosphoric acid; 200MHz Brucker Spectrometer) investigation methods were used in order to check out the purity of as prepared products. T.N URSALEŞ, E-J POPOVICI, I. SILAGHI-DUMITRESCU, N. POPOVICI and A.URSALEŞ

3. Results and discussions The starting calixarenes were prepared by adapting the synthesis method described in the literature7-9. The simultaneous alkylation of calixarenes with dichlorophenilfosphin oxide and crotyl bromide give rise to some derivatives that possess two types, of substituting groups at the lower rim (reaction 1).

I. R = t-Bu; R’ = Crotyl; n = 1; m = 2; II. R = t-Bu; R’ = Crotyl; n = 1; m = 4; III. R = t-Bu; R’ = Crotyl; n = 1; m = 6 Elemental analysis, 1H-NMR, 31P-NMR and FT-IR (figure 1-3) investigations confirmed the formation of the new calix[n]arenes derivatives The main characteristics of the new products are as follows: Compound I

Elemental analysis: MW=862, calculated for C58H71O4P; C= 79.02 %; H= 8.49%, P= 4.23 % found; C= 80.74 %; H= 8.24%, P= 3.59% calculated. -1 -1 -1 FT-IR: (KBr, cm ); CH=CH: 3023.84 and 965.68 cm ; P=O: 1201.43 cm ; P-O-C: -1 -1 970.00 cm ; P-C: 694.25 cm ; 1 H-NMR (ppm, CDCl3, ppm): 6.75-7.24(m, 13H, C6H2 and C6H5); 5.60-5.80(m, 4H, CH=CH); 4.23-4.42(m, 8H, ArCH2Ar); 2.86-3.40(m, 4H, -OCH2); 0.69-1.78(m, 42H, =CH-CH3 and tBu). 31 P-NMR (ppm, CDCl3, ppm): 22.85; and –10.42 (2 s, 1P). Compound II

Elemental analysis: MW=1294, calculated for C88H111O4P; C= 80.01 %; H= 8.69%, P= 3.21 % found; C= 81,61 %; H= 8.57%, P= 2.39% calculated. -1 -1 -1 FT-IR: (KBr, cm ): CH=CH: 3021.91 and 966.64 cm ; P=O: 1203.36 cm ; P-O-C: -1 -1 955,64 cm ; P-C: 694.98 cm ; 1 H-NMR (ppm, CDCl3, ppm): 6.93-7,26(m, 17H, C6H2 and C6H5); 5.62(m, 8H, 3 CH=CH); 3.86(m, 12H, ArCH2Ar); 1.85(m, 8H,-OCH2); 1.55(d, 8H, JHH=7,12Hz); 1.26(s, 54H, tBu). 31 P-NMR (ppm, CDCl3, ppm): 22.62 (s, 1P). Compound III

Elemental analysis: MW=1726, calculated for C118H151O4P; C= 81.79 %; H= 8.92%, P= 2.29 % found; C= 82.04 %; H= 8.75%, P= 1.79% calculated. -1 -1 -1 FT-IR: (KBr, cm ): CH=CH: 3023.84 and 968.57 cm ; P=O: 1204.81 cm ; P-O-C: -1 -1 947.84 cm ; P-C: 693.28 cm ; 1 H-NMR (ppm, CDCl3, ppm: 7.49(m, 5H, C6H5); 6.94(s, 16H, C6H2); 5.50(m, 12H, 3 3 CH=CH); 4.08(d, 8H, ArCH2Ar, JHH=6,9Hz);3.72(d, 8H, ArCH2Ar, JHH= 7,08Hz); 3 2.70(m, 12H, -OCH2); 1.45(d, 18H, =CH-CH3, JHH=6,0Hz); 1.25(s, 72H, tBu). SYNTHESIS AND CHARACTERISATION OF SOME NEW CALIX[n]ARENE DERIVATIVES

31 P-NMR (ppm, CDCl3, ppm): 21.84 (1s, 1P). In the 1H-NMR spectra of the parent calixarenes, the OH group signals appear at 9.5-10.2 ppm. The disappearance of the signals in the spectra of the new derivatives confirmed the full functionalisation of the starting calixarenes.

Figure 1. FT-IR spectra of mono(phenylphosphinoxide)-bis(2-butenyl)-p- tertbutylcalix[4]arene (I) (straight line) as compared with the original p- tertbutylcalix[4]arene (dashed line).

Figure 2. Infrared spectra of mono(phenylphosphinoxide)-tetra(2-butenyl)-p- tertbutylcalix[6]arene (II) ( straight line) as compared with the original p- tertbutylcalix[6]arene (dashed line).

Figure 3. Infrared spectra of mono(phenylphosphinoxide)-hexa(2-butenyl)-p- tertbutylcalix[8]arene (III) (straight line) as compared with the original p- tertbutylcalix[8]arene (dashed line).

T.N URSALEŞ, E-J POPOVICI, I. SILAGHI-DUMITRESCU, N. POPOVICI and A.URSALEŞ

New signals at 5.5-5.8 ppm appeared, which were correlated with the presence of the protons from the CH=CH groups of the crotyl groups. The protons

of -OCH2 and =CH-CH3 groups give signal at ~ 1.8-2.8 ppm and near the tert-butyl protons, respectively. The protons from the phenylphosphinoxide bridge give broad signals in the aromatic zone of the calixarene skeleton (6.7-7.5 ppm). The phosphorus presence in the new compounds was put in evidence by the specific signals (21.84-22.85 ppm) from the 31P-NMR spectra. FTIR spectra revealed the disappearance of the OH groups from the parent calixarenes. The specific OH vibrations of the p-tert-butylcalix[4]arene, p-tertbutylcalix[6]arene and p-tertbutylcalix[8]arene (3173, 3150 or 3140 cm-1, correspondingly) could not been noticed in the spectra of the compound I, II or III. New vibration bands for the substituting groups could be observed, namely: 1201.43 cm-1 (P=O), 970.00 cm-1 (P-O-C) and 3023.84 and 965.68cm-1 (crotyl groups) for compound I; 1203 cm-1 (P=O), 956 cm-1 (P-O-C) and 3022 cm-1 and 967 cm-1 (crotyl groups) for compound II and 1201 cm-1 (P=O), 970 cm-1 (P-O-C), and 3024 cm-1 and 966 (crotyl groups) for compound III.

4. Conclusions The spectroscopic investigations confirmed the formation of calixarenes derivatives containing one phenylphosphinoxide bridge group and 2, 4 or 6 crotyl groups, respectively. These new compounds, which were not previously described in the literature, possess large utilisation potential. The presence of “p” electrons of the oxygen (P=O group) and π electrons (crotyl group) could increase the ability of the new calixarene derivatives to extract rare-earth ions.

Acknowledgements: The work was supported by CERES National Research Program, under contract no. 42/2001. REFERENCES 1. C.D.Gutsche, “Calixarenes revisited” , Royal Society of Chemistry, London, 1998, p.3. 2. R.Ungaro, “Calixarenes in Action”, Imperial College Press, London, 2000, p.1. 3. V.Böhmer, Calixarene-Makrocyclen mit (fast) unbegrenzten Moglichkeiten, Angew. Chem., Int.Ed.Engl., 1995, 34, p.713. 4. V.W.Yam, K.K.W.Lo , “Recent advances in utilization of transition metal complexes and lanthanides as diagnostic tools”, Coordination Chem. Reviews, 1999, 184, p.157. 5. E.M.Georgiev, N.Wolf, D.M.Roundhill , “Lower rim alkylamonium-substituted calix[4]arenas as –proton-switchable- extractants for chromate and dichromate anions” , Polyhedron, 1997, 16, p.1581. 6. L.J.Bauer, C.D.Gutsche, “Calixarenes 15. The formation of Complex of Calixarenes with Neutral Organic Molecules in Solution” , J.Am.Chem.Soc., 1985, 107, p.6063. 7. C.D.Gutsche, M.Iqbal , “P-tert-butylcalix[4]arene” , Org.Synthesis, 1989, 68, p.234. 8. C.D.Gutsche, B.Dhawan, M.Leonis, D.Stewart , “P-tert-butylcalix[6]arene”, Org. Synthesis, 1989, 68, p. 238. 9. J.H.Munch, C.D.Gutsche, “P-tert-butylcalix[8]arene”, Org. Synthesis, 1989, 68, p.243.