Fullerene complexes with divalent metal dithiocarbamates: structures, magnetic properties, and photoconductivity

A series of complexes of fullerenes C-60 and C-70 with metal dithiocarbamates {M-II(R(2)dtc)(2)}center dot C-m (m = 60 or 70) and metal dithiocarbamates coordinated to nitrogen-containing ligands (L), {M-II(R(2)dtc)(2))(x)center dot L}center dot C-60 (x = 1 or 2), where M = Cu, Zn, Cd, Hg, Mn, or Fe, R = Me, Et, Pr-n, Pr-i, or Bu-n, L is 1,4-diazabicyclo[2.2.2] octane (DABCO), N,N'-dimethylpiperazine, or hexamethylenetetramine, were synthesized. The shape of dithio- carbamate molecules is sterically compatible with the spherical shape of C60, resulting in an efficient interaction between their p systems. The resulting compounds are characterized by a layered or three-dimensional packing of the fullerene molecules. In the C-60 complexes, iron(II) and manganese(II) dithiocarbamates exist in the high-spin states (S = 2 and 5/2). The magnetic susceptibility of {M-II(Et(2)dtc)(2)}(2)center dot C-m (M = Fe or Mn, m = 60 or 70) in the temperature range of 200 - 300 K is described by the Curie - Weiss law with T = - 250 and - 96 K and with maxima at 110 and 46 K, respectively, which is indicative of a strong antiferromagnetic spin coupling between M-II. The Weiss constants for the [{M-II(Et(2)dtc)(2)}(2)center dot DABCO]center dot C-60 center dot(DABCO)(2) complexes (M = Fe or Mn) are 1.7 and 0.3 K, respectively. The magnetic moments of the complexes containing Fe and Mn dithiocarbamates slightly increase at temperatures below 50 and 35 K, respectively, which is evidence of the ferromagnetic spin coupling between MII in M-II(Et(2)dtc)(2)}(2)center dot DABCO. Single crystals of the complexes exhibit low dark conductivity ( 10 - 10 - 10 - 11 S cm - 1). The visible light irradiation of these crystals leads to an increase in the photocurrent by two - three orders of magnitude. The photogeneration of free charge carriers in the complexes occurs both due to the photoexcitation of metal dithiocarbamate (Cu-II(Et(2)dtc)(2)) and through the charge transfer from metal dithiocarbamate (M-II(Et(2)dtc)(2), M = Zn or Cd) to C-60.