Rational Design of a 3D MnII -Metal-Organic Framework Based on a Nonmetallated Porphyrin Linker for Selective Capture of CO2 and One-Pot Synthesis of Styrene Carbonates.

A 3D MnII -porphyrin metal-organic framework (MOF), [{Mn2 (TCPP)⋅2H2 O}⋅DMF]n (MOF1) (TCPP=5,10,15,20-tetrakis(4-benzoate)porphyrin), was constructed; it exhibits an interesting 3D framework structure with two types of 1D channels of dimensions of 3.94×8.37 Å2 and 4.66×4.93 Å2 running along the crystallographic a axis. Owing to the presence of a nonmetallated porphyrin cavity, MOF1 exhibits selective storage of CO2 with an isosteric heat of adsorption value of 32.1 kJ mol-1 , which is further supported by theoretical calculations with the calculated binding energy (BE) of 29.78 kJ mol-1 . Interestingly, the nonmetallated nature of the porphyrin ligand was exploited for implantation of coordinatively unsaturated FeIII ions to generate a FeIII @MOF1 framework, which acts as an efficient recyclable catalyst for the oxidation of styrenes to the corresponding epoxides in the presence of PhIO as an oxidant at room temperature. Moreover, the one-pot synthesis of styrene carbonates from styrenes and CO2 was also achieved using FeIII @MOF1 as a catalyst. The rational design of a porous MnII -porphyrin MOF for the selective capture of CO2 and the one-pot synthesis of styrene carbonates at mild conditions is reported.

Construction of 3-Fold-Interpenetrated Three-Dimensional Metal-Organic Frameworks of Nickel(II) for Highly Efficient Capture and Conversion of Carbon Dioxide.

A series of three new isostructural metal-organic frameworks (MOFs) of nickel(II), [{Ni(muco)(bpa)(2H2O)}·2H2O] (1), [{Ni(muco)(bpe)(2H2O)}·2.5H2O] (2), and [{Ni(muco)(azopy)(2H2O)}·2H2O] (3) [where muco = trans,trans-muconate dianion, bpa = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-bis(4-pyridyl)ethylene, and azopy = 4,4'-bis(azobipyridine)], have been synthesized and characterized by single-crystal X-ray diffraction analysis and other physicochemical methods. Compounds 1-3 exhibit an interesting 3-fold-interpenetrated three-dimensional pillar-layered framework structure constituted of 4-coordinating (4-c) NiII nodes with {66}-neb net topology. Remarkably, in spite of 3-fold interpenetration, the structures possess one-dimensional channels with dimensions of ∼8.05 × 5.25 Å2. Gas (N2, Ar, H2, and CO2) adsorption studies of compounds 2 and 3 revealed selective adsorption properties for CO2 over other gases. In all three structures, the 4-c NiII node has two coordinated H2O molecules that can be reversibly removed by high-temperature treatment to generate a dehydrated framework composed of highly unsaturated, Lewis acidic NiII ions. Further, the activated compounds of 1-3 act as efficient recyclable catalysts for heterogeneous cycloaddition of CO2 with styrene oxide, resulting in cyclic carbonate with high conversion and selectivity. Interestingly, the cycloaddition reactions of CO2 with bulky epoxides show a decrease in the activity with an increase in the alkyl chain length of the substrate due to confinement of the pore size of the MOF. The high catalytic efficiency and size-dependent selectivity for smaller epoxides show the potential utility of 1 as a promising heterogeneous catalyst for the cycloaddition of CO2. Furthermore, the catalyst can be easily separated and reused for several cycles without significant reduction in the catalytic activity as well as structural rigidity. Compounds 1-3 represent rare examples of interpenetrated MOFs exhibiting selective storage and conversion of CO2 at mild conditions.

Ruthenium(ii) arene NSAID complexes: inhibition of cyclooxygenase and antiproliferative activity against cancer cell lines.

Non-steroidal anti-inflammatory drugs (NSAIDs) are a group of molecules which have been found to be active against cancer cells with chemopreventive properties by targeting cyclooxygenase (COX-1 and COX-2) and lipoxygenase (LOX), commonly upregulated (particularly COX-2) in malignant tumors. Arene ruthenium(ii) complexes with a pseudo-octahedral coordination environment containing different ancillary ligands have shown remarkable activity against primary and metastatic tumors as reported earlier. This work describes the synthesis of four novel ruthenium(ii)-arene complexes viz. [Ru(η6-p-cymene)(nap)Cl] 1 [Hnap = naproxen or (S)-2-(6-methoxy-2-naphthyl)propionic acid], [Ru(η6-p-cymene)(diclo)Cl] 2 [Hdiclo = diclofenac or 2-[(2,6-dichlorophenyl)amino] benzeneacetic acid, [Ru(η6-p-cymene)(ibu)Cl] 3 [Hibu = ibuprofen or 2-(4-isobutylphenyl)propanoic acid] and [Ru(η6-p-cymene)(asp)Cl] 4 [Hasp = aspirin or 2-acetoxy benzoic acid] using different NSAIDs as chelating ligands. Complexes 1-3 have shown promising antiproliferative activity against three different cell lines with GI50 (concentration of drug causing 50% inhibition of cell growth) values comparable to adriamycin. At the concentration of 50 µM, complex 3 is more effective in the inhibition of cyclooxygenase and lipooxygenase enzymes, followed by complex 2 and complex 1 in comparison to their respective free NSAID ligands indicating a possible correlation between the inhibition of COX and/or LOX and anticancer properties. Molecular docking studies with COX-2 reveal that complexes 1 and 2 having naproxen and diclofenac ligands exhibit stronger interactions with COX-2 than their respective free NSAIDs and these results are in good agreement with their relative experimentally observed COX inhibition as well as anti-proliferative activities.

Fine tuning through valence bond tautomerization of ancillary ligands in ruthenium(ii) arene complexes for better anticancer activity and enzyme inhibition properties.

Four new ruthenium arene PTA type complexes have been synthesized using substituted picolinamide derivatives as ancillary ligands and characterized by spectroscopic methods. In one of the complexes, the ancillary ligand has shown an unprecedented valence-bond tautomerization in the presence of an ammonium salt to act as a polar neutral donor ligand making the ligand more prone towards substitution. The same compound has shown remarkable antiproliferative activity against three cancer cell lines with GI50 values comparable to Adriamycin, a known therapeutic drug. Along with this it also strongly inhibits the action of thioredoxin reductase, which might be a probable reason for the enhanced proliferative action of the valence-bond tautomerized compound.