Supramolecular structures from three new molecular building blocks based on the protonation/deprotonation of 3,3-bis(2-imidazolyl)propionic acid (HBIP): [H3BIP](C4O4)center dot H2O, [Cu(HBIP)(2)](HC4O4)(2), and [Cu(BIP)(2)]center dot 2H(2)O

摘要

This paper reports the synthesis. structure solution, and electronic and electron paramagnetic resonance (EPR) characterization of three new HBIP-containing compounds (HBIP = 3,3-bis(2-imidazolyl)propionic acid): [H3BIP](C4O4)center dot H2O (1), [Cu(HBIP)(2)](HC4O4)2 (2). and [Cu(BIP)(2)]center dot 2H(2)O (3). The structure of 1. resulting from the cocrystallization of [H3BIP](2+) and SQ(2-), is made up of squarate anions, diprotonated HBIP, and water molecules packed together by multiple-path H-bonding into a supramolecular 3D network. Compounds 2 and 3 constitute the first cases of structurally characterized Cu(II)-HBIP/BIP complexes in which the ligand acts in a tridentate chelating fashion. They consist of Jahn-Teller elongated octahedral mononuclear Cu(II) units packed to-ether into a 3D network driven in each case by a different set of multiple H-bonding paths. These differences in the supramolecular crystal packing of 2 and 3 arise from the different nature of the uncoordinated counterparts, HSQ(-) in 2 vs H2O in 3, which play a critical role in the set of H-bonding interactions. The use of simple anion templation to modify the network topology is discussed. Electronic and EPR spectra are indicative of an essentially d(x)2-(y)2 ground state for the copper(II) ions in 2 and 3.