Habibar Chowdhury

Two new hexacoordinated coordination polymers of cadmium(II) containing bridging units only: Syntheses, structures and molecular properties

AbstractThe syntheses, characterizations and structures of a neutral 2D coordination polymer [Cd(bnzd)(NCS)2]n (1) and a polycationic 3D coordination polymer isolated as perchlorate salt [Cd(bnzd)3]n(ClO4)2n (2) (bnzd = benzidine) are described. X-ray structural analyses reveal that each hexacoordinated cadmium(II) center in 1 adopts a distorted octahedral geometry with a CdN4S2 chromophore bound by two N atoms of two different bnzd units and two N and two S atoms of symmetric doubly bridged end-to-end NCS − units extended in a 2D sheet. Six N atoms of six different bridged bnzd units are bonded to each cadmium(II) in 2 in a non-ended fashion affording a 3D network structure. In the crystalline state, each 2D sheet structure in 1 is further stabilized by π⋯π interaction which in turn affords a 3D network structure through multiple intermolecular N-H ⋯S hydrogen bonds. On the other hand, the 3D network structure in 2 is stabilized by weak intermolecular N-H ⋯O hydrogen bonds and C-H ⋯π interactions. Bnzd, 1 and 2 display intraligand 1(π- π*) fluorescence in DMF solution at room temperature. Graphical AbstractTwo cadmium(II) coordination polymers of benzidine with or without thiocyanate afford varied metal-organic frameworks (MOFs) through multiple weak non-covalent forces and are good luminous materials.

Two manganese(II) coordination polymers driven by (iso)nicotinoyl-hydrazone blocks and pseudohalide ancillary ligands: syntheses, structural features, and magnetic properties

Abstract Two coordination polymers, [Mn2(μ-L1)2(μ-N3)2]n (1) and [Mn(μ-HL2)(SCN)2]n (2), were assembled in a single-pot from MnCl2·4H2O, HL1 (2-acetylpyridine isonicotinoylhydrazone) or HL2 (2-acetylpyridine nicotinoylhydrazone) and ancillary ligand sources (NaN3 or NH4NCS). The products were fully characterized, including by single-crystal X-ray diffraction, which revealed a 2-D metal–organic layer in 1 and a 1-D zigzag coordination chain in 2. Both 1 and 2 are constructed from six-coordinate Mn(II) nodes that adopt distorted octahedral (MnN5O) environments; the adjacent nodes are driven by the μ-L1 and μ-N3 linkers in 1 or μ-HL2 linkers in 2 to form different metal–organic networks. Their topological classification was performed, disclosing the hcb and 2C1 topology in 1 and 2, respectively. Different weak non-covalent interactions promote dimensionality extension. Variable-temperature magnetic susceptibility measurements were carried out, revealing weak ferromagnetic and antiferromagnetic interactions in 1 and 2, respectively.