title: High Tc ferrimagnetic organic-inorganic hybrid materials with MnII-L-MnII and MnII-NC-NbIV linkages (L=pyrazine, pyrazine-N,N'-dioxide, bipyrimidine).
abstract: A series of heterobimetallic, cyano-bridged 3D inorganic-organic hybrid networks with MnII-L-MnII and MnII-NC-NbIV linkages are reported. Reaction of [Mn(H2O)6]2+ with [Nb(CN)8]4- in the presence of organic linker L (pyrazine (pyz), pyrazine-N,N'-dioxide (pzdo), and 2,2'-bipyrimidine (bpym)) in H2O affords {MnII2(pz)2(H2O)4[NbIV(CN)8]}.pz.3H2O (1), {MnII2(pzdo)(H2O)4[NbIV(CN)8]}.5H2O (2), and {MnII2(bpym)(H2O)2[NbIV(CN)8]} (3), respectively. 1-3 were examined by X-ray crystallography and vibrational and magnetochemical studies. 1 is characterized by the coexistence of 3D inorganic cyano-bridged and 1D organic [Mn-(micro-pyz)]n2n+ sublattices along with the presence of monocoordinated and crystallization molecules of pyrazine. Assemblies 2 and 3 exhibit dimeric {MnII2-(micro-L)}4+ coordination motifs. The magnetic behavior of heterobimetallic 1-3 complexes is dominated by antiferromagnetic coupling between MnII and NbIV centers mediated by cyano bridges, resulting in long-range ferrimagnetic ordering with a high TC of 27 (1), 37 (2), and 50 K (3). The magneto-structural correlation leads to the conclusion that the magnitude of TC is related to the type of coordination polyhedra of [Nb(CN)8] moieties (SAPR (1), intermediate between SAPR and DD (2), and DD (3)), the relative number of cyano bridges per Mn2Nb unit, and coexistence of inorganic and organic connectivity. FC/ZFC responses appear to be sensitive to the degree of organic connectivity. The discussion of magneto-structural correlation is based on the spin-density properties of adequate heterobimetallic systems containing octacyanometalates.
authors.affiliation: Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland. podgajny@chemia.uj.edu.pl
authors.forename: Robert
authors.initials: R
authors.lastname: Podgajny
authors.forename: Dawid
authors.initials: D
authors.lastname: Pinkowicz
authors.forename: Tomasz
authors.initials: T
authors.lastname: Korzeniak
authors.forename: Wojciech
authors.initials: W
authors.lastname: Nitek
authors.forename: Michał
authors.initials: M
authors.lastname: Rams
authors.forename: Barbara
authors.initials: B
authors.lastname: Sieklucka