A spirobenzopyran-quinoline (SBPQ) based sensor was synthesized which selectively detects trivalent ions viz. Al(3+), Fe(3+) and Cr(3+) through a fluorescence turn on signal in the red region (~675 nm) with the detection limit in the order of 10(-8) M. The potentiality of the probe was confirmed by employing it for fluorescence bio-imaging with Al(3+) in three different types of live-cells.

Reaction between PdCl(2) and 1-alkyl-2-(arylazo)imidazole (RaaiR') or 1-alkyl-2-(naphthyl-alpha/beta-azo)imidazole (alpha/beta-NaiR') under reflux in ethanol has isolated complexes of compositions Pd(RaaiR')(2)Cl(2) (5, 6) and Pd(alpha/beta-NaiR')(2)Cl(2) (7, 8). The X-ray structure determination of one of the molecules, Pd(alpha-NaiBz)(2)Cl(2) (7c), has reported a trans-PdCl(2) configuration, and alpha-NaiBz acts as monodentate N(imidazole) donor ligand. The spectral (IR, UV-vis, (1)H NMR) data support the structure. UV light irradiation (light source: Perkin-Elmer LS 55 spectrofluorimeter, Xenon discharge lamp, lambda = 360-396 nm) in a MeCN solution of the complexes shows E-to-Z isomerization of the coordinated azoimidazole unit. The reverse transformation, Z-to-E, is very slow with visible light irradiation. Quantum yields (phi(E-->Z)) of E-to-Z isomerization are calculated, and phi is lower than that of the free ligand but comparable with those of Cd(II) and Hg(II) complexes of the same ligand. The Z-to-E isomerization is a thermally induced process. The activation energy (E(a)) of Z-to-E isomerization is calculated by controlled-temperature experimentation. cis-Pd(azoimidazole)Cl(2) complexes (azomidazole acts as N(imidazole) and N(azo) chelating ligand) do not respond upon light irradiation, which supports the idea that the presence of noncoordinated azo-N to make free azo (-N=N-) function is important to reveal photochromic activity. DFT calculation of Pd(alpha-NaiBz)(2)Cl(2) (7c) has suggested that the HOMO of the molecule is constituted of Pd (32%) and Cl (66%), and hence photo excitation may use the energy of Pd and Cl instead of that of the photofunctional -N=N-Ar motif; thus, the rate of photoisomerization and quantum yield decrease versus the free ligand values.

Two rare examples of azo anion diradical complexes of Rh(III) are reported. These complexes showed excellent memory switching properties with a large ON/OFF ratio and are suitable for RAM/ROM applications. Their electronic structures have been elucidated using a host of physical methods, including X-ray crystallography, variable-temperature magnetic susceptibility measurement, cyclic voltammetry, electron paramagnetic resonance spectroscopy, and density functional theory. The results indicate a predominant triplet state description of the systems with two ferromagnetically coupled radicals.

A mononucleating (HL(1)) and a dinucleating (HL(2)) "end-off" compartmental ligand have been designed and synthesized by controlled Mannich reaction using p-cresol and bis(2-methoxyethyl)amine, and their formation has been rationalized. Six complexes have been prepared on treating HL(1) and HL(2) with Zn(II)X2 (X = Cl(-), Br(-), I(-)) with the aim to investigate their hydrolytic activity on phosphoester bond cleavage. Interestingly, the mononucleating ligand was observed to yield dinuclear complexes, [Zn2(L(1))2X2] (1-3), while the potential dinucleating ligand generated mononuclear complexes, [Zn(HL(2))X2] (4-6). Four (1-4), out of six complexes studied, were characterized by single-crystal X-ray diffraction (XRD): the Zn ion exhibits trigonal bipyramidal and tetrahedral coordination spheres in the di- and mononuclear complex, respectively. The hydrolytic kinetics, followed spectrophotometrically with 4-nitrophenylphosphate (4-NPP) in buffered dimethylformamide (DMF) (97.5% DMF, v/v) because of solubility reasons, under excess substrate conditions (substrate:complex = 20:1), indicated that the complexes enormously accelerate the rate of phosphomonoester hydrolysis with first order rate constants (kcat) in the range 2-10 s(-1) at 25 °C. In each case kinetic data analyses have been run by Michaelis-Menten treatment. The efficacy in the order of conversion of substrate to product (p-nitrophenolate ion) follows the trend 1 > 2 > 3 > 4 > 5 > 6, and the ratio of kcat of an analogous dinuclear to mononuclear complex is ≃2. An electrospray ionization-mass spectrometry (ESI-MS) study has revealed the dissociation of the centrosymmetric dinuclear complex to two mononuclear species instead of a syn-cooperative catalysis. Density functional theory (DFT) calculations have been performed to rationalize our proposed mechanistic pathway for phosphatase activity. The comparative analysis concludes the following facts under experimental conditions: (1) the halide bound to the active site affects the overall rate in the order: Cl(-) > Br(-) > I(-) regardless of nuclearity; (2) dinuclear complexes prevail over the mononuclear ones.