Multifunctional Zn(II) Coordination Polymer as Highly Selective Fluorescent Sensor and Adsorbent for Dyes

A new Zn(II)-based coordination polymer (1) comprising the Schiff base ligand obtained by the condensation of 5-aminosalicylic acid and salicylaldehyde has been synthesized. This newly synthesized compound has been characterized by analytical and spectroscopic methods, and finally, by single-crystal X-ray diffraction technique in this study. The X-ray analysis reveals a distorted tetrahedral environment around the central Zn(II) center. This compound has been used as a sensitive and selective fluorescent sensor for acetone and Ag⁺ cations. The photoluminescence measurements indicate that in the presence of acetone, the emission intensity of 1 displays quenching at room temperature. However, other organic solvents caused meagre changes in the emission intensity of 1. Additionally, the fluorescence intensity of 1 has been examined in the presence of different ketones viz. cyclohexanone, 4-heptanone, and 5-nonanone, to assess the interaction between the C=O group of the ketones and the molecular framework of 1. Moreover, 1 displays a selective recognition of Ag⁺ in the aqueous medium by an enhancement in its fluorescence intensity, representing its high sensitivity for the detection of Ag⁺ ions in a water sample. Additionally, 1 displays the selective adsorption of cationic dyes (methylene blue and rhodamine B). Hence, 1 showcases its potential as an excellent luminescent probe to detect acetone, other ketones, and Ag⁺ with an exceptional selectivity, and displaying a selective adsorption of cationic dye molecules.

Crystal structure of 4-[(3-meth-oxy-2-oxidobenzyl-idene)azaniumyl]-benzoic acid methanol monosolvate

In the crystal of the title compound, C15H13NO4·CH3OH, the Schiff base mol-ecule exists in the zwitterionic form; an intra-molecular N-H⋯O hydrogen bond stabilizes the mol-ecular structure. The benzene rings are nearly co-planar, subtending a dihedral angle of 5.34 (2)°. In the crystal, classical O-H⋯O and weak C-H⋯O hydrogen bonds link the Schiff base mol-ecules and methanol solvent mol-ecules into a three-dimensional supra-molecular architecture. The crystal studied was refined as an inversion twin.

Diaqua-bis-{2-hy-droxy-5-[(pyridin-2-yl)methyl-idene-amino]-benzoato-κN,N'}zinc(II) dihydrate

The complex mol-ecule of the title compound, [Zn(C(13)H(9)N(2)O(3))(2)(H(2)O)(2)]·2H(2)O, has 2 symmetry with the Zn(II) cation located on a twofold rotation axis. The Zn cation is N,N'-chelated by two 5-[(pyridin-2-yl)methyl-idene-amino]-2-hy-droxy-benzoate anions and coordinated by two water mol-ecules in a distorted octa-hedral geometry. Within the anionic ligand, the pyridine ring is oriented at a dihedral angle of 49.54 (10)° with respect to the benzene ring. The carboxyl-ate group of the anionic ligand is not involved in coordination but is O-H⋯O hydrogen bonded to the coordinated and uncoordinated water mol-ecules. Weak inter-molecular C-H⋯O hydrogen bonding is also present in the crystal structure.

Design and synthesis of heterobimetallic topoisomerase I and II inhibitor complexes: in vitro DNA binding, interaction with 5'-GMP and 5'-TMP and cleavage studies

New potential cancer chemotherapeutic complexes Cu-Sn(2)/Zn-Sn(2) 3 and 4 were designed and prepared as topoisomerases inhibitors; their in vitro DNA binding studies were carried out which reveal strong electrostatic binding via phosphate backbone of DNA helix, in addition to other binding modes viz. coordinate covalent and partial intercalation. To throw insight to molecular binding event at the target site, UV-vis titrations of 3 and 4 with mononucleotides of interest, viz, 5'-GMP and 5'-TMP were carried out, (in case of 4) by (1)H and (31)P NMR. Cleavage studies employing gel electrophoresis demonstrate both the complexes 3 and 4 are efficient cleavage agents and are specific groove binders (complex 3 binds to both major and minor groove while complex 4 is specifically minor groove binder only). In addition, the complexes show high inhibition activity against topoisomerase I and II. However, complex 4 exhibits significant inhibitory effects on the Topo I activity at a very low concentration approximately 2.5 microM.