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RESEARCH PRODUCT

Structural, magnetic, and spectroscopic comparative studies on four new derivatives of DIMMAL (2-di1H-2-imidazolylmethylmalonate): a novel generator of multidimensional networks.

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This paper reports the synthesis, structure solution, and magnetic characterization of four new DIMMAL-containing compounds (H 2 DIMMAL = 2-di1H-2-imidazolylmethylmalonic acid), H 2 DIMMAL.H 2 O (1), Na 2 (DIMMAL).5H 2 O (2), [Cu(HDIMMAL) 2 ] (3), and [Cu 2 (DIMMAL) 2 (H 2 O) 2 ].2H 2 O (4). Compound 1, containing two carboxylates and two protonated imidazole rings, adopts the dizwitterion configuration. These monohydrate MBBs pack together into a 3D array driven, as in the other three cases herein reported, by a combination of multiple-path H-bonds and aromatic-aromatic interactions. Compound 2 consists of centrosymmetric Na + tetramers in which four NaO 6 distorted octahedra are interconnected by carboxylate and water bridges. Compound 3 consists of mononuclear [Cu(HDIMMAL) 2 ] units in which HDIMMAL - acts as a tridentate ligand through two imidazole N atoms and the deprotonated O from a carboxylate. Compound 4 consists of centrosymmetric cyclic dinuclear [Cu 2 (DIMMAL) 2 -(H 2 O) 2 ].2H 2 O units involving propionate-arm bridges. The building-block units described above, in each case, are interconnected into 3D networks by multiple H-bonding paths and aromatic-aromatic interactions. The EPR spectra are indicative of an essentially d x 2 - y 2 ground state for the copper(ll) ions in 3 and 4 (CuN 4 O 2 and CuN 2 O 2 O' chromophores, respectively). Magnetic susceptibility measurements in the range of 1.8-200 K for compound 4 show weak antiferromagnetic exchange between the copper(ll) ions (2J = -1.6(1) cm-1). The effectiveness of the propionate-arm bridges, involving C-C a bonds, in propagating magnetic exchange between the copper(ll) ions is discussed.