Synthesis, crystal structure and properties of N- tert-butyliminodiacetic acid (H 2TEBIDA), [Cu(TEBIDA)(H 2O) 2], {[Cu(TEBIDA)(Him)]·2H 2O} n, {Cu(TEBIDA) (5MeHim)·H 2O} n, and [Cu(TEBIDA)(2,2′-bipy)(H 2O)]·4.5H 2O, (Him=imidazole, 5MeImH=5-methylimidazole and 2,2′-bipy=2,2′-bipyridine)

Abstract

N- tert-butyliminodiacetic acid (H 2TEBIDA, compound 1) has been prepared and characterised by thermogravimetric analysis, FT-IR and NMR spectra, and X-ray crystallography (final R 1=0.04). The zwitterion H 2TEBIDA ± is intra-stabilised by a hydrogen bond, and H-bonded chains of zwitterions form supramolecular 2D bilayers with tert-Bu groups towards the external faces. Compounds [Cu(TEBIDA)(H 2O) 2] ( 2), {[Cu(TEBIDA)(Him)]·2H 2O} n ( 3) {[Cu(TEBIDA)(5MeHim)]·H 2O} n ( 4) [Cu(TEBIDA)(bipy)]·4.5H 2O ( 5) were also obtained and studied by thermal, (FT-IR, reflectance and ESR) spectral, magnetic and X-ray diffraction methods. Compound 2 has a molecular structure and TEBIDA with mer-NO 2 tridentate conformation in contrast with that reported for {[Cu(IDA)(H 2O) 2]} n (polymeric chains, elongated octahedral Cu(II) coordination and fac-NO+O(apical) IDA conformation). Compounds 3 and 4 form zig–zag polymeric chains and follow all structural co-relations reported for complexes with equimolar Cu(II)/iminodiacetato (IDA)/ N-heterocyclic donor ratio (Cu(II) coordination type 4+1, mer-NO 2 TEBIDA conformation and N(Him-like) donor in trans to the Cu–IDA-like bond). However, compound 5 has an unexpected fac-O 2+N(apical) TEBIDA conformation, with the aqua ligand (instead of one N-heterocyclic donor) in the trans-site of the CuN(IDA-like) bond, in contrast with structural co-relations for complexes with Cu/(IDA or IDA-like)/ N-heterocyclic donor ratio 1/1/2 and closely related compounds ( fac-NO+O(apical) IDA-like conformation and one N-heterocyclic donor in the trans-site to the CuN(IDA-like) bond). These findings are attributed to the influence of π,π-stacking interactions involving both rings of two 2,2′-bipy ligands in the molecular recognition process, forming pairs of complex molecules which probably build the crystal of compound 5 with non-coordinated water.