Kamal Kumar Bisht - Synthesis, Magnetic Properties, and Structural Investigation of Mixed-Ligand Cu(II) Helical Coordination Polymers with an Amino Acid Backbone and N-Donor Propping: 1-D Helical, 2-D Hexagonal Net (hcb), and 3-D ins Topologies

Version 1

      Publication Details (including relevant citation   information):

      Cryst. Growth Des., 2011, 11 (5), pp 1631–1641

      DOI: 10.1021/cg101587h

      Publication Date (Web): March 16, 2011

      Abstract:

      Three Cu(II) coordination polymers, {[Cu(l-cysteate)(1,4-Bix)(H2O)]·H2O}n  (1), {[Cu(l-aspartate)(1,4-Bix)0.5]·H2O}n  (2), and {[Cu(l-aspartate)(4,4′-Bpy)0.5]H2O}n  (3), have been synthesized solvothermally,   employing enantiopure l-amino   acids and bidentate N-donor ligands,   1,4-bis(imidazol-1-ylmethyl)benzene (1,4-Bix) and   4,4′-bipyridyl(4,4′-Bpy), to yield 1-D, 2-D, and 3-D helical   coordination polymers, respectively. All the three neutral   frameworks are well-characterized by various physicochemical   methods (C,H,N analysis, IR, TGA) including the single crystal   X-ray diffraction technique. The chiral nature of complexes   2 and 3 was established using   solid state CD spectra. Structural investigation of complex   1 revealed 1-D helical chains, whereas that of   complex 2 confirms a chiral and helical   two-dimensional 63-hcb net, with   helicity propagating in both the dimensions. Cu(II) nodes with   the mixed ligands in complex 3 generate a   three-dimensional framework by the pillaring of Cu(l-aspartate) 2-D helical layers by 4,4′-Bpy   units, identified as a (3,4)-coordinated binodal net with   (63)(65.8)-ins topology.   The temperature-dependent magnetic properties of the l-aspartic acid derived for complexes   2 and 3 were studied in detail.   Complex 2 showed weak antiferromagnetic   behavior, which matches well with the crystallographic parameters   (syn−anti conformation of carboxylate bridged Cu(II),   with lowest Cu−Cu distance 5.367 Å). Similarly, complex   3, with a shorter and rigid N-donor ligand,   4,4′-Bpy, and the carboxylate group of the amino acid moiety   linking the adjacent metal centers in the   synanti conformation, also displayed a weak   antiferromagnetic behavior at lower temperatures, showing the   weak exchange couplings between Cu(II) centers.

      Address (URL): http://pubs.acs.org/doi/abs/10.1021/cg101587h