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Synthesis, Crystal Structures, and Magnetic Properties of Two Novel Cyanido-Bridged Heterotrimetallic {CuIIMnIICrIII} Complexes
journal contribution
posted on 2017-02-08, 16:23 authored by Maria-Gabriela Alexandru, Diana Visinescu, Sergiu Shova, Marius Andruh, Francesc Lloret, Miguel JulveThe
self-assembly process between the heteroleptic [CrIII(phen)(CN)4]− and [CrIII(ampy)(CN)4]− metalloligands and the heterobimetallic {CuII(valpn)MnII}2+ tecton afforded two
heterotrimetallic complexes of formula [{CuII(valpn)MnII(μ-NC)2CrIII(phen)(CN)2}2{(μ-NC)CrIII(phen)(CN)3}2]·2CH3CN (1) and {[CuII(valpn)MnII(μ-NC)2CrIII(ampy)(CN)2]2·2CH3CN}n (2) [phen = 1,10-phenanthroline, ampy = 2-aminomethylpyridine,
and H2valpn = 1,3-propanedyilbis(2-iminomethylene-6-methoxyphenol)].
The crystal structure of 1 consists of neutral CuII2MnII2CrIII4 octanuclear units, where two [Cr(phen)(CN)4]− anions act as bis-monodentate ligands through cyanide
groups toward two manganese(II) ions from two [CuII(valpn)MnII]2+ units to form a [{Cu(valpn)Mn}2Cr2(CN)4]6+ square motif. Two [Cr(phen)(CN)4]− pendant anions in 1 are
bound to the copper(II) ions with cis–trans geometry with respect to the bridging [Cr(phen)(CN)4]− anion. Compound 2 is a sheet-like coordination
polymer, where chains constituted by {CrIII(ampy)(CN)4} spacers act as bis-monodentate ligands toward the manganese(II)
ions belonging to the {CuII(valpn)MnII} nodes,
which are interlinked by another {CrIII(ampy)(CN)4} unit that acts as a bridge between the copper(II) and manganese(II)
ions of adjacent chains. Magnetic susceptibility measurements in the
temperature range of 1.9–300 K were performed for 1 and 2. An overall antiferromagnetic behavior is observed
for 1, the ground spin state being described by a spin
triplet from the square motif plus two magnetically isolated spin
triplets from the two peripheral chromium(III) ions. Ferrimagnetic
chains with interacting spins 1/2 (resulting spin of the trimetallic
{CuII(valpn)MnII(μ-NC)CrIII} fragment) and 3/2 (spin from the bis-monodentate
[CrIII(ampy)(CN)4]− with weak
interchain ferromagnetic interactions across the cyanide bridge between
the chromium(III) and the copper(II) ion from adjacent chains [θ
= +3.83(2) cm–1]) occur in 2, resulting
into a ferromagnetic ordering below 3.5 K. The values of the magnetic
coupling between the Cu(II) and Mn(II) ions through the double phenoxide
bridge [J = −63.1(2) (1) and
−62(3) cm–1 (2)] and those between
the Cr(III) and the Mn(II) across the single cyanide bridge [J = −7.08(5) and −4.86(6) cm–1 (1) and −8.59(3) cm–1 (2)] agree with the values reported for these exchange pathways
in other magnetostructural studies.