Coordination polymers derived from a bis-pyridyl-bis-amide ligand: Supramolecular structural diversities and anion binding properties

Coordination Polymers as a Functional Material for the Selective Molecular Recognition of Nitroaromatics and ipso-Hydroxylation of Arylboronic Acids

We report the synthesis and structural characterization of two coordination polymers (CPs), namely; [{Zn(L)(DMF)₄ } ⋅ 2BF₄ ]_α (1) and [{Cd(L)₂ (Cl)₂ } ⋅ 2H₂ O]_α (2) (where L=N² ,N⁶ -di(pyridin-4-yl)naphthalene-2,6-dicarboxamide). Crystal packing of 1 reveals the existence of channels running along the b- and c-axis filled by the ligated DMF and lattice anions, respectively. Whereas, crystal packing of 2 reveals that the metallacycles of each 1D chain are intercalating into the groove of adjacent metallacycles resulting in the stacking of 1D loop-chains to form a sheet-like architecture. In addition, both 1 and 2 were exploited as multifunctional materials for the detection of nitroaromatic compounds (NACs) as well as a catalyst in the ipso-hydroxylation of aryl/heteroarylboronic acids. Remarkably, 1 and 2 showed high fluorescence stability in an aqueous medium and displayed a maximum 88% and 97% quenching efficiency for 4-NPH, respectively among all the investigated NACs. The mechanistic investigation of NACs recognition suggested that the fluorescence quenching occurred via electron as well as energy transfer process. Furthermore, the ipso-hydroxylation of aryl/heteroarylboronic acids in presence of 1 and 2 gave up to 99% desired product yield within 15 min in our established protocol. In both cases, 1 and 2 are recyclable upto five cycles without any significant loss in their efficiency.

New Bis-Pyrazole-Bis-Acetate Based Coordination Complexes: Influence of Counter-Anions and Metal Ions on the Supramolecular Structures

A new flexible bis-pyrazol-bis-acetate ligand, diethyl 2,2’-(pyridine-2,6-diylbis (5-methyl-1H-pyrazole-3,1-diyl))diacetate (L), has been synthesised, and three coordination complexes, namely, [Zn(L)2](BF4)2 (1), [MnLCl2] (2) and [CdLCl2] (3) have been obtained. All ligands and complexes were characterised by IR, mass spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. Single crystal X-ray diffraction experiment revealed that the primary supramolecular building block of 1 is a hexagonal chair shaped 0D hydrogen bonded synthon (stabilised by C–H∙∙∙O hydrogen bonding and C=O∙∙∙π interactions), which further built into a 2D corrugated sheet-like architecture having a 3-c net honeycomb topology, and finally extended to a 3D hydrogen bonded network structure having a five nodal 1,3,3,3,7-c net, through C–H∙∙∙F interactions. On the other hand, the two crystallographically independent molecules of 2 exhibited two distinct supramolecular structures such as 2D hydrogen bonded sheet structure and 1D zigzag hydrogen bonded chain, sustained by C–H∙O and C–H∙∙∙Cl interactions, which are further self-assembled into a 3,4-c network structure, and 3 showed a 2D hydrogen bonded sheet structure. The supramolecular structural diversity in these complexes is due to the different conformations adopted by the ligands, which are mainly induced by different metal ions with coordination environments controlled by different anions. Hirshfeld surface analysis was explored for the qualitative and quantitative analysis of the supramolecular interactions.

Selective recognition of Fe3+ and CrO42− ions using a Zn(ii) metallacycle and a Cd(ii) coordination polymer and their heterogeneous catalytic application

A Zn(ii) metallacycle [Zn₂{(L)₂(DMF)₂(NO₃)₂}]·(NO₃)₂ (1) along with a Cd(ii) coordination polymer [{Cd(L)₂(DMF)₂}·(NO₃)₂]_n (2) have been synthesized, structurally characterized and exploited as a multifunctional material.

Crystal engineering of a series of complexes and coordination polymers based on pyrazole-carboxylic acid ligands

Three new complexes and two coordination polymers have been synthesized.

Is metal metathesis a framework-templating strategy to synthesize coordination polymers (CPs)? Transmetallation studies involving flexible ligands

Framework-templating strategy, where Cd-CP acted as template to preorganise the linkers, resulted in a Cu-CP, which was not obtained by direct reaction of Cu(ii) and the ligand.

A novel two-dimensional metal-organic supramolecular framework including π-π stacking and hydrogen-bond interactions

[μ-N,N'-Bis(pyridin-3-yl)benzene-1,4-dicarboxamide-1:2κ(2)N:N']bis{[N,N'-bis(pyridin-3-yl)benzene-1,4-dicarboxamide-κN]diiodidomercury(II)}, [Hg2I4(C18H14N4O2)3], is an S-shaped dinuclear molecule, composed of two HgI2 units and three N,N'-bis(pyridin-3-yl)benzene-1,4-dicarboxamide (L) ligands. The central L ligand is centrosymmetric and coordinated to two Hg(II) cations via two pyridine N atoms, in a syn-syn conformation. The two terminal L ligands are monodentate, with one uncoordinated pyridine N atom, and each adopts a syn-anti conformation. The HgI2 units show highly distorted tetrahedral (sawhorse) geometry, as the Hg(II) centres lie only 0.34 (2) or 0.32 (2) Å from the planes defined by the I and pyridine N atoms. Supramolecular interactions, thermal stability and solid-state luminescence properties were also measured.

Self-assembled metallo-macrocycle based coordination polymers with unsymmetrical amide ligands

A series of metallo-macrocyclic based coordination polymers has been prepared from flexible amide ligands N-6-[(3-pyridylmethylamino)carbonyl]-pyridine-2-carboxylic acid (L1-CH(3)) and N-6-[(4-pyridylmethylamino)carbonyl]-pyridine-2-carboxylic acid (L2-CH(3)). In all but one case, self-assembled dinuclear metallo-macrocyclic units form the basis of the polymeric structures, whereby discrete metal centres, and dinuclear or trinuclear clusters, are linked by the self-assembled macrocycles to give 1D and 2D coordination polymers. In one instance, a 1D coordination polymer is formed in a reaction carried out under ambient conditions; when the same reaction is conducted under solvothermal conditions a 2D structure is formed. In all but two of these structures, the polymeric chains and nets are close-packed within the crystals. In the case of a 6,3-connected 2D coordination polymer {[Cd(3)(L2-CH(3))(3)(NO(3))(L2)(CH(3)OH)](NO(3))(2)·12½H(2)O}(n) (9), small oval channels percolate down the a-axis of the unit cell.