A 2D coordination polymer assembled from a nickel(11) tetraazamacrocyclic cation and 4,4'-(dimethylsilanediyl)diphthalate(3) linker

The preformed nickel(II) complex of the 14 -membered macrocyclic ligand 1,4,8,11-tetraazacyclotetradecane (cyclam, L), when treated with 4,4'-(dimethylsilanediyl)diphthalic acid (H4A) in a DMF/H20 mixture (4:1 v/v) under heating, leads to [Ni(L)]3(HA)2.3DMF (I-DMF). Redissolution of this compound in a DNEF/H20/Me0H mixture (4:1:30 v/v/v) with mild acidification under gentle heating results in the formation of a similar compound but containing water and methanol molecules of crystallization, [Ni(L)]3(HA)2.5H20-2Me0H (II -H20). At lower temperature and concentration of reactants and longer reaction time, single crystals of composition {[{Ni(L)}3(HA)21-4CH3OHI, (II-Me0H) were isolated. Single -crystal X-ray diffraction analysis of this compound, which, according to PXRD is isostructural with II -1120 but different from I-DMF, revealed its two-dimensional (2D) polymeric structure, i.e. poly[[bis{3-4-[(4carboxy-3-carboxylatophenyl)climethylsilyl]benzene-1,2-dicarboxylato-K301:02:031- tris (1,4,8,11 -tetr aazacyclotetradecane-K4N)trinickel (II)] methanol tetrasolvate], {[Ni3(C18111308Si)2(CioH24N4)31-4CH30111,. It is built up of the monoprotonated tricarboxylate HA3- ligand coordinated in a monodentate manner in the axial positions of two crystallographically independent Ni" cations, one of which is located on a crystallographic inversion centre. Both metal ions adopt a slightly tetragonally elongated trans -N402 octahedral geometry. The compound has a lamellar structure with polymeric layers oriented parallel to the (102) plane, which are in turn linked via hydrogen bonds involving protonated carboxylic acid groups of the ligand. Bulk compounds I-DMF and II -1120 were characterized by FT-IR and diffuse reflectance spectroscopy and thermogravimetry, which provide evidence of their structural differences.