Photochemical Formation of Ferrimagnetic Chains from a Pair of Polymeric Complexes Made of Octahedral Bis(hexafluoroacetylacetonato)manganese(II) with Diazodi(4-pyridyl)methane in the Cis and Trans Configurations as Repeating Units

Two kinds of 1:1 manganese complexes a and b of bis(hexafluoroacetylacetonato)manganese(II)
coordinated with diazodi(4-pyridyl)methane (1) were prepared. Complexes a and b crystallize in the
orthorhombic space group Pbca and in monoclinic C2/c, respectively. Two pyridyl nitrogen atoms from two
different molecules of 1 are coordinated in the cis and trans configurations to the manganese ion to form
helical and zigzag infinite chains of octahedral manganese complexes in complexes a and b, respectively.
The magnetic susceptibilities (χmol) of both crystals before and after irradiation were measured on a SQUID
susceptometer and revealed χmolT vs T plots characteristic of ferrimagnetic chains after irradiation for 97 h;
interaction between the manganese(II) ion and the photogenerated carbene is antiferromagnetic in both
complexes. The antiferromagnetic exchange coupling parameters (J) in the photolyzate of complex a and b
were estimated by a theoretical treatment through a procedure of extrapolation by using small rings to be J/kB
= −34.8 ± 0.8 and −24.4 ± 0.5 K, respectively. Maximum χmolT values of 210 at 5 K for cis- and 246
emu·K·mol-1 at 1.9 K for trans complexes correspond to correlation lengths of 186 and 218 manganese−carbene S = 3/2 units, respectively.