Syntheses, Crystal Structures, and Magnetic Properties of Four New Cyano-Bridged Bimetallic Complexes Based on the mer-[Fe^III(qcq)(CN)₃]⁻ Building Block

Abstract

Four new cyano-bridged bimetallic complexes, [{Mn(III)(salen)}2{Fe(III)(qcq)(CN)3}2]n·3nCH3CN·nH2O (1) [salen = N,N'-ethylenebis(salicylideneiminato) dianion; qcq(-) = 8-(2-quinoline-2-carboxamido)quinoline anion], [{Mn(III)(salpn)}2{Fe(III)(qcq)(CN)3}2]n·4nH2O (2) [salpn = N,N'-1,2-propylenebis(salicylideneiminato)dianion], [{Mn(II)(bipy)(CH3OH)}{Fe(III)(qcq)(CN)3}2]2·2H2O·2CH3OH (3) (bipy = 2,2'-bipyridine), and [{Mn(II)(phen)2}{Fe(III)(qcq)(CN)3}2]·CH3CN·2H2O (4) (phen = 1,10-phenanthroline) have been synthesized and characterized both structurally and magnetically. The structures of 1 and 2 are both unique 1-D linear branch chains with additional structural units of {Mn(III)(salen/salpn)}{Fe(III)(qcq)(CN)3} dangling on the sides. In contrast, 3 and 4 are cyano-bridged bimetallic hexanuclear and trinuclear clusters, respectively. The intermolecular short contacts such as π-π interactions and hydrogen bonds extend 1-4 into high dimensional supermolecular networks. Magnetic investigation reveals the dominant intramolecular antiferromagnetic interactions in 1, 3, and 4, while ferromagnetic and antiferromagnetic interactions coexist in 2. Alternating current measurement at low temperature indicates the existence of slow magnetic relaxation in 1 and 2, which should be due to the single ion anisotropy of Mn(III).

Various Structural Types of Cyanide-Bridged FeIII–MnIII Bimetallic Coordination Polymers (CPs) and Polynuclear Clusters Based-on A New mer-Tricyanoiron(III)Building Block: Synthesis, Crystal Structures, and Magnetic Properties

“…The Fe atom is complexed by three CN groups and three N donors of qxcq in a meridional configuration, forming octahedral coordination geometry. The Fe–C bonds are in the normal range compared with other reported mer -tricyanoiron(III) precursors [24,25,26,27,28,29,30,31,32,33,34]. One of the three Fe–N amide bond lengths with the value 1.945(5) Åwas slightly shorter than the other ones (2.004(5)–2.060(5) Å) relevant with qxcq, which can be attributed tothe strong σ-donor influence of the deprotonated amide ligand.…”

“…Up to now, many 0D discrete clusters and 1D infinite coordination polymers have been successfully obtained by assembling the decorated polycyanometallates such as the blocked trans -dicyano-, fac -tricyano-, mer -tricyano- and tetracyanometallate, and the paramagnetic compound with or without the auxiliary ligand [18,19,20,21,22,23]. Several reports from our and other groups on the mer -[Fe(L](CN) 3 ] -/2- -based cyanide-bridged complexes, where L represents the equatorial in-plane ligands with relative large steric effect for efficiently lowering the dimensionality of the target complex such as bis (2-pyridylcarbonyl)amidate (bpca) [24,25], 8-(pyridine-2-carboxamido)quinoline (pcq) [26,27,28], 8-(pyrazine-2-carboxamido)quinoline (pzcq) [29], 8-(5-methylpyrazine-2-carboxamido)quinoline (mpzcq) [30], 8-(2-quinoline-2-carboxamido)quinoline (qcq) [31], N -(quinolin-8-yl)isoquinoline-1-carboxamide anion (iqc) [32], and bis (2-benzimidazolyl)pyridine (bbp) [33,34] showed that the mer -[Fe(L](CN) 3 ] -/2- type precursors are excellent candidates for constructing interesting magnetic assemblies. Here, a new structurally characterized mer -tricyanoiron(III) building block 1 (Scheme 1) was first employed to assemble with the manganese Schiff base compounds (Scheme 1), leading to a series of new CN-bridged Fe(III)-Mn(III) complexes with various structural types formulated as {[Fe(qxcq)(CN) 3 ][Mn(L 1 )(H 2 O)]}[Mn(L 1 )(H 2 O)(CH 3 OH)](ClO 4 )·1.5MeOH·0.5H 2 O (L 1 = N,N′-bis (3-methoxy-5-bromosalicylideneiminate) (2), {[Fe(qxcq)(CN) 3 ][Mn(L 2 )]} 2 ·0.5H 2 O (L 2 = N,N′ -ethylene- bis (3-ethoxysalicylideneiminate)) (3), [Fe(qxcq)(CN) 3 ][Mn(L 3 )] (L 3 = bis (acetylacetonato)ethylenediimine) (4), and [Fe(qxcq)(CN) 3 ][Mn(L 4 )]·1.5MeOH·0.5CH 3 CN·0.25H 2 O (L 4 = N,N′ -(1,1,2,2-tetramethylethylene)bis(salicylideneiminate)) ( 5 ).…”

Tuning of chain chirality by interchain stacking forces and the structure–property relationship in coordination systems constructed by meridional FeIII cyanide and MnIII Schiff bases

“…These studies showed that the coupling constant is contingent on the Mn-NuC bending in the bridging pathway. [25][26][27][28][29][30][31][32][33][34] In comparison, mer-Fe tricyanides have been developed to collect information on basic magnetic properties. The Fe precursors have been used to react with anisotropic Mn(III) Schiff bases, leading to the formation of Mn(III)-Fe(III) bimetallic chain complexes with molecular or one-dimensional structures.…”