Synthesis, spectroscopy and magnetic properties of cis-(9,10-dihydro-9-oxo-10-acridineacetato-μ-O)copper(II). An unusual carboxylate-bridged chain with very weak magnetic exchange

Abstract

The synthesis, crystal structure, spectroscopic and magnetic properties are reported for Cu(CMA) 2(H 2O) 2, where CMA − is the 9,10-dihydro-9-oxo-10-acridineacetate ion. The complex C 30H 24N 2O 8Cu crystallizes in the monoclinic space group C2/ c, with cell dimensions a=17.700(7), b=19.266(8), c=7.424(4) Å, β=91.88(4)°, Z=4. The structure was solved by direct methods and refined to a final R value of 0.035. The structure of Cu(CMA 2)(H 2O) 2 consists of unusual one-dimensional polymers which contain zigzag (CuO 2CuO 2) chains and stacks of acridone moieties. The 9,10-dihydro-9-oxo-10-acridineacetate ion coordinates in the monodentate manner. Each copper ion shows distorted (4+2) octahedral coordination. The four short bonds come from two acetate oxygen and two water oxygen atoms. The long apical bonds are to the basal acetate oxygen atoms from neighboring copper centers. The angle at the oxygen, in the planar Cu 2O 2 unit is 109.4(1)°, the CuCu distance is 3.967(3) Å. The hydrogen atoms of each water molecule bind with the non-coordinated acetate oxygen atoms and 9-oxo oxygen atoms of the neighboring polymer. The acridone rings overlap with a 3.35 Å interlayer separation. The magnetic susceptibility of the compound has been examined between 4.2 and 300 K. The compound behaves as an S=1/ 2 paramagnet. The absence of coupling arises from the unfavorable relative orientation of the magnetic orbitals. The EPR and LF spectra are typical of the distorted octahedral environment of copper(II) ion.