Two isostructural metal-organic framework (MOF) materials, namely, {[MeSi((3)Py)3]6(Cu6I6)}n (1) and {[ MeSi((3)Qy)3]6(Cu6I6)}n (2), featuring Cu6I6 clusters were synthesized from tridentate arylsilane ligands of the type MeSi((3)Py)3 ((3)Py = 3-pyridyl) and MeSi((3)Qy)3 ((3)Qy = 3-quinolyl), respectively. While the MOF 1 displays the usual thermochromism associated with traditional Cu4I4Py4 clusters, the MOF 2 shows (3)XLCT/(3)MLCT emission due to the Cu6I6 cluster core at both 298 and 77 K, albeit with some marginal variations in its emission wavelengths. Interestingly, an unusual reversal in the mechanochromic luminescent behavior was observed for these isostructural MOFs at 298 K wherein a pronounced blue-shifted high energy emission for 1 (from orange to yellowish-orange) and a red-shifted low-energy emission for 2 (from green to orange) were obtained upon grinding these samples. This is primarily due to the variations in their cuprophilic interactions as 1 displays shorter Cu···Cu distances (2.745(1) Å) in comparison with those present in 2 (3.148(0) Å). As a result, the ground sample of 2 exhibits a prominent red shift in luminescence owing to the reduction of its Cu···Cu distances to an unknown value closer to the sum of van der Waals radii between two Cu(I) atoms (2.80 Å). However, the blue-shifted emission in 1 is presumably attributed to the rise in its lowest unoccupied molecular orbital energy levels caused by changes in the secondary packing forces. Furthermore, the absorption and emission characteristics of 1 and 2 were substantiated by time-dependent density functional theory calculations on their discrete-model compounds. In addition, the syntheses, reactivity studies, and photophysical properties of two one-dimensional MOFs, namely, {[MeSi((3)Qy)3]2(Cu2I2)}n (3) and {[MeSi((3)Qy)3](CuI)}n (4), having dimeric Cu2I2 and monomeric CuI moieties, respectively, were examined.

A metal-free cross-dehydrogenative coupling between quinoxalinones (sp C-H) and amines (N-H) in the presence of catalytic iodine is reported. The reaction yields 3-aminoquinoxalinones in moderate to high yields under ambient conditions in dioxane as solvent and aqueous tert-butyl hydroperoxide (TBHP) as the terminal oxidant. The reaction is highly versatile and exhibits good functional group tolerance with a range of primary and secondary amines. It provides a practical access to pharmaceutically active 3-aminoquinoxalinone derivatives. Preliminary mechanistic studies reveal in situ iodination of the amine as the putative mode of activation.

The octahedral cage assembly [CoLCl(HO)]Cl has been synthesized in a single-step reaction by using a polypyridyl-functionalized tripodal silane ligand. The electrochemical behavior of the cage in water exhibits the pH dependence of potential as well as catalytic current indicating the possible involvement of proton-coupled electron transfer in H evolution. Electrocatalytic hydrogen evolution from an aqueous buffered solution gave a turnover frequency of 16 h. Further, this cage assembly has been explored as a photocatalyst (blue light irradiation λ 469 nm) for the evolution of H from water in the presence of Ru(bpy) as a photosensitizer and ascorbic acid as a sacrificial electron donor. This catalytic reaction is found to be pseudo first order with a turnover frequency of 20.50 h.

A novel three-dimensional coordination network 1 in a new 4,5,6-connected topology (4,5,6T115) built from linear CuCl(HO) clusters and tetrahedral tetrakis(3-pyridyl)vinylsilane ligands is reported. Utilizing a similar tetrahedral ligand, tetrakis(3-pyridyl)ethylsilane, a different framework 2 having CuCl(HO) clusters is obtained in tcs topology. The activated sample of 1 shows an excellent and reversible uptake of I in solid as well as in solution phases owing to the presence of uncoordinated chloride ions and electron rich vinylic groups in it. The I uptake studies on the anion-exchanged samples, of bromide, iodide, and nitrate ions, show a progressive decrease in the adsorption capacity with the sample containing uncoordinated Cl ion showing a maximum uptake of 48.5% and the one with the NO ions exhibiting the lowest uptake of 24.0%. These observations suggest that the halide counterions interact better with I in comparison with nitrate ions and the better I uptake in the presence of Cl ions over the other two halides is due to its smaller size that offers a larger surface area for adsorption. Also, both these compounds were shown to be useful catalysts for the solvent-free syntheses of bis(indolyl)methanes via Friedel-Crafts alkylation reaction.

A series of novel oxazolidinone antibacterials with diverse fused heteroaryl C-rings bearing hydrogen bond donor and hydrogen bond acceptor functionalities were designed and synthesized. The compound with benzoxazinone C-ring substructure () exhibited superior activity compared to linezolid against a panel of Gram-positive and Gram-negative bacteria. Structural modifications at C5-side chain of resulted in identification of several potent compounds (, ,, and ). Selected compounds and showed very good microsomal stability and no CYP liability, thus clearing preliminary safety hurdles. A docking model of binding to 23S rRNA suggested that the increased potency of is due to additional ligand-receptor interaction.

An attractive catalytic pathway for the conversion of water to oxygen would involve two metal oxide centers combining in a constructive sense to make OO. This prospect makes the study of certain dinuclear transition metal complexes particularly attractive. In this work, we describe the design and synthesis of two symmetrical bis-tridentate polypyridine ligands 6 and 12 that bind two Ru II centers at a separation of 3.6 Å in 7 and 5.7 Å in 13. In the presence of Ce IV at pH = 1, these systems oxidize water with the system having the more proximal metals being more reactive. In the case of the more proximal metal centers, the bridging ligand is a 3,6-disubstituted pyridazine which, under the influence of Ce IV , cleaves into two [Ru(bpc)(pic) 2 CH 3 CN] + fragments ( 14) which then function as the actual catalyst (bpc = 2,2′-bipyridine-6-carboxylate, pic = 4-methylpyridine). The second dinuclear catalyst contains a central pyrimidine ring which is less sensitive to oxidative decay and hence less reactive. Caution is advised in the use of Ce IV as a sacrificial electron acceptor due to unexpected oxidative decay of the catalyst.

Synthesis of new cyclotetrasiloxane scaffolds containing peripherally functionalized 3-pyridyl moieties, [MeSiO(CH═CH(3)Py)]4 (L(1)) and [MeSiO(CH2CH2(3)Py)]4 (L(2)), and their reactivity studies with certain d(10) metal ions are reported. The ligand L(1) is obtained by the Heck-coupling reaction of tetramethyl tetravinyl tetrasiloxane (D4(vi)) and 3-bromopyridine in the presence of the Pd(0) catalysts. The as-synthesized ligand L(1) shows the presence of three stereoisomers, cis-trans-cis (L(1A)), cis-cis-trans (L(1B)), and all-trans (L(1C)), which are quantitatively separated by column chromatography. Subsequent reduction of L(1A), L(1B), and L(1C) with triethylsilane in the presence of catalytic amounts of Pd/C leads to the formation of the ligands L(2A), L(2B), and L(2C) with retention of stereochemistry due to the precursor moieties. Treatment of ZnI2 with L(1A) gives a one-dimensional coordination framework [(L(1A))4(ZnI2)2]∞, 1. These 1D-chains are further connected by π-π stacking interactions between the pyridyl groups of the adjacent chains leading to the formation of a three-dimensional network with the topology of a PtS net. The reaction of silver nitrate with ligand L(1B) gives a chain like one-dimensional cationic coordination polymer {[(L(1B))4Ag2]·2NO3·H2O·CH3OH }∞, 2, consisting of two different kinds of 32-membered macrocycles. Treatment of the all-trans ligand L(2C) with copper(I) iodide salt results in the formation of a cubane-type Cu4I4 cluster MOF [(L(2C))4Cu4I4]∞, 3, in a two-dimensional 4-connected uninodal sql/Shubnikov tetragonal plane net topology represented by the Schläfli symbol {4(4).6(2)}. This MOF displays a thermochromic luminescence behavior due to Cu4I4 clusters showing an orange emission at 298 K and a blue emission at 77 K.

By utilizing L 1 , a cationic 2D-MOF {[(L 1) 2 (Cu 6 I 5)](OH) • 3DMF • 4MeOH} n , 1 containing a rugby ball shaped discrete Cu 6 I 5 cluster has been reported earlier. Formation of a new 3D-MOF {[(L 2) 2 (Cu 6 I 4)](OH) 2 • 2DMF} n containing a Zintl type [(Cu 6 I 4) 2+ ] n cluster chains is reported in this paper. A neutral cluster MOFs 3 with formula unit of {[Cu 4 I 4 L 3 (CH 3 CN)] • 2DMF • 3H 2 O} n has been prepared from the ligand L 3. Formation of the smaller Cu 4 I 4 clusters in the MOF 3 is due to the presence of a MeCN ligation at one of the Cu(I) atoms which not only precludes the extension of the assembly in three dimension but also reduces the size of the obtained cluster. Unlike 1 which showed a ligand-assisted thermochromism, photophysical studies on the 3D-MOF 2 exhibited green phosphorescence at both 298 K and 77 K. The occurrence of the phosphorescence at 77 K in 2 is due to triplet cluster centered (3 CC) excited state of the cluster as there is no ligand-centered transition observed at 298 K. The 2D-MOF 3 does not show any characteristic luminescence behavior as the presence of the acetonitrile coordination at one of the Cu(I) ion is believed to quench the emission by non-radiative pathways. Further, luminescence quenching experiments on 1 and 2 with aromatic nitro-analytes showed a very high sensing selectivity for picric acid (TNP) over other aromatic nitro-analytes.