Cr(pyrazine)2(OSO2CH3)2: A two-dimensional coordination polymer with an antiferromagnetic ground state

Abstract

A novel two-dimensional (2D) coordination polymer with the formula Cr(pyrazine)2(OSO2CH3)2 has been synthesized and characterized. Powder X-ray diffraction data reveal that this material, which crystalizes in the Pnnm orthorhombic space group, is composed of rectangular grid layers with octahedral CrN4O2 nodes and pyrazine vertices. Since the redox-active pyrazine ligand can be reduced in the presence of transition metals, X-ray absorption spectroscopy and quantum chemical calculations were used to confirm the +II oxidation state of the Cr center. Magnetic susceptibility measurements indicate the presence of antiferromagnetic interactions between the chromium(II) centers through the neutral pyrazine and suggest an antiferromagnetic ordered state below TN ≈ 10 K, which was confirmed by heat-capacity measurements.

Ligand field-actuated redox-activity of acetylacetonate

“…This behavior is typical for linear Heisenberg chains with antiferromagnetic interactions between identical, adjacent spins, and observed in other antiferromagnetically coupled Cr(II) systems. 27 No anomalies suggesting long-range magnetic order in neither cT vs. T nor M vs. H were found. In contrast to 1, the room temperature cT products for 2-4 are all close to 1.0 cm 3 K mol À1 reecting an S T ¼ 1 ground state ( Fig.…”

Supramolecular structures of terbium(iii) porphyrin double-decker complexes on a single-walled carbon nanotube surface

“…The gure displays that the magnetic susceptibility c steadily decreases by increasing the applied magnetic eld and the temperature increase which indicates the presence of predominant antiferromagnetic interactions, that's in agreement with the reported results. 86 Thereof, in addition to the presence of iron catalyst particles, there is also possibility that SWNT shows magnetic response to the applied magnetic eld which seems to be happened in our SWNT sample and resulted in the remarkable opened hysteresis loop in Fig. S11g.…”

Unusually Strong Long-range Electronic Coupling Across Redox-Active Bridges in M3+/M4+ Mixed-Valence Complexes of Group 4 Congeners

“…Multimetallic complexes, or complexes in which metal ions are bridged by ligands having multiple coordination sites, are species that have garnered widespread interest owing to their applications, which range from molecular electronics [1][2][3][4][5][6] and photovoltaics [7][8][9] to catalysis [10][11][12][13][14][15][16][17] and biomimetics. [18][19][20][21] One area of intense research activity has been the development of molecular wires, 1-2, 7, 22-24 or molecules that facilitate electron transfer and can ultimately be used for charge separation and transfer [25][26][27][28] or as building blocks for molecular devices.…”

“…[29][30] Overwhelmingly, inorganic/organic hybrid species developed as molecular wires feature so-called redox-active ligands as the bridging species. 5,[31][32][33][34][35] This trend is likely due to noninnocence displayed by these systems, whereby admixing of the ligand frontier orbitals and d-orbitals of the coordinated metal ion yield the requisite electronic delocalization for wire-like behavior, [36][37][38][39][40][41][42] and electronic cooperativity between the metal and ligand can provide additional stability during electron transfer. [43][44][45][46][47] The ligands of choice for these systems largely feature endocyclic imine moieties, such as pyrazine, 5,[48][49][50][51] pyridine, 22,[25][26][52][53][54][55][56] and porphyrin functionalities.…”

“…5,[31][32][33][34][35] This trend is likely due to noninnocence displayed by these systems, whereby admixing of the ligand frontier orbitals and d-orbitals of the coordinated metal ion yield the requisite electronic delocalization for wire-like behavior, [36][37][38][39][40][41][42] and electronic cooperativity between the metal and ligand can provide additional stability during electron transfer. [43][44][45][46][47] The ligands of choice for these systems largely feature endocyclic imine moieties, such as pyrazine, 5,[48][49][50][51] pyridine, 22,[25][26][52][53][54][55][56] and porphyrin functionalities. 37,[57][58][59][60][61] It is well established that bidentate exocyclic imines, such as αdiimine ligands, display electronic delocalization when coordinated to various metal centers.…”