Tj. Neal et al., Molecular structures and magnetochemistry of two (beta-oxooctaethylchlorinato)copper(II) derivatives: [Cu(oxoOEC)] and [Cu(oxoOEC(center dot))]SbCl6, INORG CHEM, 38(19), 1999, pp. 4294-4302
The preparation and characterization of the beta-oxochlorin derivative [3,3
,7,8,12,13,17,18-octaethyl-(3H)-porphin-2-onato(2 -)]copper(II), [Cu(oxoOEC
)], and its,pi-cation radical derivative, [Cu(oxoOEC(.))][SbCl6], are descr
ibed. Both compounds have been characterized by single-crystal X-ray struct
ure determinations; IR, UV/vis/near-IR, and EPR spectroscopies; and tempera
ture-dependent magnetic susceptibility measurements. Crystals of [Cu(oxoOEC
)] have two crystallographically distinct molecules, one at a general posit
ion ([Cu(oxoOEC)]-gen) and a second at a special position ([Cu(oxoOEC)]-spe
). [Cu(oxoOEC)]-gen has a S-4-saddled conformation whereas [Cu(oxoOEC)]-spe
has a modest ruffled conformation. [Cu(oxoOEC(.))][SbCl6] shows a cofacial
dimeric unit in the solid state, with a mean plane separation of 3.41 Angs
trom and a lateral shift of 5.47 Angstrom. Crystal data for [Cu (oxoOEC)]:
monoclinic, space group C2/c, Z = 12, a = 38.404(8) Angstrom, b = 14.692(6)
Angstrom, c = 16.977(11) Angstrom, beta = 101.46(2)degrees Crystal data fo
r [Cu(oxoOEC(.))][SbCl6]: triclinic, space group P (1) over bar, Z = 2, a =
13.063(1) Angstrom, b = 14.108(2) Angstrom, c = 11.486(2) Angstrom, alpha
= 93.77(3)degrees, beta = 102.17(1)degrees, gamma = 74.07(1)degrees. The EP
R spectrum of [Cu(oxoOEC(.))][SbCl6] in frozen dichloromethane at 77 K show
s the characteristics of a dimeric copper(II) triplet state. Two broad, con
centration-dependent near-IR "dimer bands" appear at 1285 and 1548 nm for [
Cu(oxoOEC(.))][SbCl6]. Solid-state magnetic susceptibility measurements for
[Cu(oxoOEC(.))][SbCl6] resulted in a large temperature dependence of the m
agnetic moments that can best be fit with a four-spin model. This model inc
ludes antiferromagnetic intermolecular copper-copper coupling (2J(Cu-Cu) =
-70 cm(-1)), antiferromagnetic radical-radical coupling (2J(r-r) = -139 cm(
-1)), and ferromagnetic intramolecular copper-radical coupling (2J(Cu-r) =
139 cm(-1)).