J. Jezierska et al., CRYSTAL-STRUCTURE, EPR AND MAGNETIC-SUSCEPTIBILITY STUDIES OF TETRAKIS[MU-(BETA-ALANINE)-O,O'] DICHLORODICOPPER(II) DICHLORO MONOHYDRATE, Inorganica Chimica Acta, 276(1-2), 1998, pp. 28-36
trabis[mu-(beta-alanine)-O,O']dichlorodicopper(II) dichloro monohydrat
e, [Cu-2(beta-alanine)(4)Cl-2]Cl-2 . H2O, crystallizes in the triclini
c system, space group P (1) over bar, a = 9.444(2), b = 9.498(2), c =
14.107(3) Angstrom, alpha = 104.04(3), beta = 105.90(3) and gamma = 97
.15(3)degrees with one formula weight in a unit cell. Two different ce
ntrosymmetric carboxylato-bridged dimeric subunits are formed. The coo
rdination geometry about each copper(II) center is square-pyramidal, w
ith four oxygen atoms in the basal plane and the chloride ion at the a
pical position. The coordination polyhedra of two dimers are slightly
different: for the dimer with a shorter Cu(l)-Cu(1)(i) distance of 2.6
331(10) Angstrom aCu(1)-Cl bond length of 2.4511(10) Angstrom is obser
ved, in comparison with Cu(2)-Cu(2)(ii) of 2.6608(10) Angstrom and Cu(
2)-Cl bond length of 2.4387(10) Angstrom for the other dimer. Magnetic
and EPR properties of the title complex are compared with those exhib
ited by [Cu-2(beta-alanine)(4)(H2O)(2)] (NO3)(4) . 4H(2)O that forms d
imeric molecules of only one kind. The isotropic exchange interactions
are strongly antiferromagnetic with a J value of 320 cm(-1) (correspo
nding to the Hamiltonian H = JS(1) . S-2) for the chloride dimers and
334 cm(-1) for the nitrate complex. The complexes exhibit spin-triplet
EPR spectra with very well-resolved hyperfine structure of two equiva
lent copper nuclei at low temperature. The chloride compound shows two
overlapping EPR spectra with different spin Hamiltonian parameters. O
nly one EPR spectrum is observed in the nitrate complex. Structural di
fferences seem to affect significantly the zero-held splitting paramet
er D. (C) 1998 Elsevier Science S.A. All rights reserved.