Synthesis, Crystal Structures, and Magnetic Properties of Two Novel Cyanido-Bridged Heterotrimetallic {CuIIMnIICrIII} Complexes

Maria-Gabriela Alexandru; Diana Visinescu; Sergiu Shova; Marius Andruh; Francesc Lloret; Miguel Julve

doi:10.1021/acs.inorgchem.6b02966

Synthesis, Crystal Structures, and Magnetic Properties of Two Novel Cyanido-Bridged Heterotrimetallic {Cu^IIMn^IICr^III} Complexes

Inorg Chem. 2017 Feb 20;56(4):2258-2269. doi: 10.1021/acs.inorgchem.6b02966. Epub 2017 Feb 8.

Authors

Maria-Gabriela Alexandru¹, Diana Visinescu², Sergiu Shova³, Marius Andruh⁴, Francesc Lloret⁵, Miguel Julve⁵

Affiliations

¹ Department of Inorganic Chemistry, Physical Chemistry and Electrochemistry, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest , 1-7 Gh. Polizu Street, 01106 Bucharest, Romania.
² Coordination and Supramolecular Chemistry Laboratory, "Ilie Murgulescu" Institute of Physical Chemistry, Romanian Academy , Splaiul Independentei 202, Bucharest 060021, Romania.
³ "Petru Poni" Institute of Macromolecular Chemistry, Romanian Academy , Aleea Grigore Ghica Vodă 41-A, RO-700487 Iasi, Romania.
⁴ Inorganic Chemistry Laboratory, Faculty of Chemistry, University of Bucharest , Str. Dumbrava Rosie 23, 020464 Bucharest, Romania.
⁵ Departament de Química Inorgànica/Instituto de Ciencia Molecular, Universitat de València , C/Catedrático José Beltrán 2, 46980 Paterna, València, Spain.

PMID: 28177230
DOI: 10.1021/acs.inorgchem.6b02966

Abstract

The self-assembly process between the heteroleptic [Cr^III(phen)(CN)₄]^- and [Cr^III(ampy)(CN)₄]^- metalloligands and the heterobimetallic {Cu^II(valpn)Mn^II}²⁺ tecton afforded two heterotrimetallic complexes of formula [{Cu^II(valpn)Mn^II(μ-NC)₂Cr^III(phen)(CN)₂}₂{(μ-NC)Cr^III(phen)(CN)₃}₂]·2CH₃CN (1) and {[Cu^II(valpn)Mn^II(μ-NC)₂Cr^III(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 Cu^II₂Mn^II₂Cr^III₄ octanuclear units, where two [Cr(phen)(CN)₄]^- anions act as bis-monodentate ligands through cyanide groups toward two manganese(II) ions from two [Cu^II(valpn)Mn^II]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 {Cr^III(ampy)(CN)₄} spacers act as bis-monodentate ligands toward the manganese(II) ions belonging to the {Cu^II(valpn)Mn^II} nodes, which are interlinked by another {Cr^III(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 {Cu^II(valpn)Mn^II(μ-NC)Cr^III} fragment) and 3/2 (spin from the bis-monodentate [Cr^III(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.