Bharat Ugale

Construction of 2D interwoven and 3D interpenetrated metal–organic frameworks of Zn(II) by varying N,N′-donor spacers

Four new metal–organic frameworks (MOFs) of Zn(II) ions, [Zn2(muco)2(azopy)2]·3DMF·2H2O (1), [Zn(muco)(bpee)]·4H2O (2), [Zn(muco)(3bpdh)] (3), and [Zn4(muco)4(4bpdh)4]·4bpdh·2H2O (4) (where, muco = trans,trans-muconate dianion, azopy = 4,4′-bisazobipyridine, bpee = 1,2-bis(4-pyridyl)ethylene, 3bpdh = 2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene, and 4bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) have been synthesized using mixed ligand systems and characterized structurally by single-crystal X-ray diffraction. Compound 1 has a 2D network with 2-fold interwoven, (4,4)-connected, {44·62}-sql net topology. Compounds 2 and 3 have 3D diamondoid (dia) structures with interesting 5-fold and 3-fold interpenetrated nets, respectively, whereas, compound 4 has a 3D cubic (pcu, α-Po) structure with 2-fold interpenetrating, 6-connected, {412·63} net topology. Topological analyses of 2 and 3 reveal 4-connected nets with 66 topology. In spite of the interweaving/interpenetration, compounds 1 and 2 possess rectangular channels with dimensions of 3.9 × 4.5 A2 and 4.3 × 7.0 A2, respectively. Photoluminescence studies showed the emissions of 1–4 and the thermal stabilities of the compounds were also examined.

Construction of 3D homochiral metal–organic frameworks (MOFs) of Cd(II): selective CO2 adsorption and catalytic properties for the Knoevenagel and Henry reaction

Two new homochiral metal–organic frameworks of Cd(II), [{Cd2(L-glu)2(bpe)3(H2O)}·2H2O] (1) and [{Cd3(L-glu)2(bpe)3(H2O)}·2NO3·H2O] (2) (where, L-glu = L-glutamate dianion, and bpe = 1,2-bis(4-pyridyl)ethylene) have been synthesized solvothermally by employing two different temperatures. Single crystal X-ray diffraction studies revealed that both 1 and 2 are homochiral and possess a 3D pillar-layered framework structure having 4,8- and 8,10-connected binodal nets with vertex symbols of {3^2.4.5^3}{3^4.4^6.5^10.6^8} and {3^11.4^28.5^5.6}2{3^8.4^18.5.6}, respectively. Interestingly, solvothermal synthesis carried out at 100 °C resulted in a 3D framework, 1 which features large rectangular 1D channels with a dimension of ∼10.38 × 4.44 A2 decorated with pendant –NH2 groups. Whereas, increasing the temperature of the reaction to 120 °C led to a non-porous highly connected 3D framework, 2 in which the –NH2 group of the L-glu ligand is coordinated to a Cd(II) node. Gas (N2, CO2, H2 and Ar) uptake studies on the dehydrated framework of 1 revealed excellent selectivity for CO2 over other gases at 273 K with a high isosteric heat of adsorption (Qst) value of 40.8 kJ mol−1. The high selectivity for CO2 gas has been attributed to the stronger interaction of CO2 with the basic –NH2 functionalized pore surface of compound 1. Furthermore, 1 acts as a very good recyclable catalyst for the carbon–carbon bond forming reactions, such as the Knoevenagel condensation and Henry reaction of benzaldehydes. Moreover, the catalyst can be easily separated from the reaction mixture and reused in four consecutive cycles without significant loss of catalytic activity and structural rigidity.

Construction of 2D interwoven and 3D metal–organic frameworks (MOFs) of Cd(II): the effect of ancillary ligands on the structure and the catalytic performance for the Knoevenagel reaction

Three new Cd(II) metal–organic networks, [{Cd(muco)(bpa)1.5}·H2O] (1), [{Cd(muco)(bpee)1.5}·7H2O] (2) and [Cd(muco)(4bpdh)·(H2O)] (3) (where, muco = trans, trans-muconate dianion, bpa = 1,2-bis(4-pyridyl)ethane, bpee = 1,2-bis(4-pyridyl)ethylene and 4bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) have been constructed using mixed ligand systems at room temperature and characterized by single-crystal X-ray diffraction and other physicochemical methods. Compounds 1 and 2 are isostructural featuring a 3D framework structure with a 5-connected, {66} net topology. Whereas, compound 3 possess an interesting 3-fold interwoven 2D network with a 4-connected, {44,62}-sql net topology. Photoluminescence measurements revealed emissions from all the three compounds owing to ligand based charge transfer (n → π* and π → π*) transitions. Catalytic investigations of the compounds for the Knoevenagel reaction unveiled the higher catalytic activity of 3 compared to that of 1 and 2. The higher catalytic performance of 3 has been attributed due to the presence of the basic azine-functionalized pore surface. Remarkably, the catalyst can be facilely separated from the reaction mixture and could be reused without significant degradation in the catalytic activity for five cycles. Compound 3 is a rare example of a 3-fold interwoven 2D network acting as an efficient recyclable heterogeneous catalyst for the Knoevenagel reaction.

Correlating Single Crystal Structure, Nanomechanical, and Bulk Compaction Behavior of Febuxostat Polymorphs

Febuxostat exhibits unprecedented solid forms with a total of 40 polymorphs and pseudopolymorphs reported. Polymorphs differ in molecular arrangement and conformation, intermolecular interactions, and various physicochemical properties, including mechanical properties. Febuxostat Form Q (FXT Q) and Form H1 (FXT H1) were investigated for crystal structure, nanomechanical parameters, and bulk deformation behavior. FXT Q showed greater compressibility, densification, and plastic deformation as compared to FXT H1 at a given compaction pressure. Lower mechanical hardness of FXT Q (0.214 GPa) as compared to FXT H1 (0.310 GPa) was found to be consistent with greater compressibility and lower mean yield pressure (38 MPa) of FXT Q. Superior compaction behavior of FXT Q was attributed to the presence of active slip systems in crystals which offered greater plastic deformation. By virtue of greater compressibility and densification, FXT Q showed higher tabletability over FXT H1. Significant correlation was found with anticipation that the preferred orientation of molecular planes into a crystal lattice translated nanomechanical parameters to a bulk compaction process. Moreover, prediction of compactibility of materials based on true density or molecular packing should be carefully evaluated, as slip-planes may cause deviation in the structure-property relationship. This study supported how molecular level crystal structure confers a bridge between particle level nanomechanical parameters and bulk level deformation behavior.

Effect of differential surface anisotropy on performance of two plate shaped crystals of aspirin form I

Abstract Differential surface anisotropy of different crystals of the same API can have a significant impact on their pharmaceutical performance. The present work investigated the impact of differential surface anisotropy of two plate‐shaped crystals of aspirin (form I) on their hygroscopicity, stability and compaction behavior. These crystals differed in their predominant facets (100) and (001) and were coded as AE‐100 & E‐001. (100) facets exposed polar carbonyl groups which provided hydrophilicity to the facets. In contrast, (001) facets possessed hydrophobicity as they exposed non‐polar aryl and methyl groups. Both the samples showed different degradation behavior, at various stability conditions (i.e. 40 °C/75%RH, 30 °C/90%RH and 30 °C/60%RH) and different time intervals. Polar groups of aspirin have been reported to be prone to hydrolysis due to which AE‐100 was less stable than E‐001. Dynamic vapor sorption (DVS) analysis at different simulated stability conditions also supported this observation, wherein AE‐100 showed higher moisture sorption than E‐001. Both the samples having similar particle size, shape, surface area and hardness value, showed differences in their compactibility. However, milling narrowed down the predominance of facets and both the milled samples showed similar stability and compaction behavior. This study was also supported by surface free energy determination, molecular modeling and face indexation of unmilled and milled samples.

Regioselective synthesis of a vitamin K3 based dihydrobenzophenazine derivative: its novel crystal structure and DFT studies

A novel acid catalyzed regioselective Michael addition of o-phenylenediamine to vitamin K3 has been carried out to synthesize a dihydrobenzophenazine derivative viz. 6a-methyl-6a,7-dihydrobenzo[α]phenazin-5(6H)-one (1). The compound has been characterized using the single crystal X-ray diffraction and density functional theory.

Synthesis, crystal structure and water oxidation activity of [Ru(terpy)(bipy)Cl]+ complexes: influence of ancillary ligands on O2 generation

Four new Ru(II) complexes, [RuII(MeMPTP)(bpy)Cl]PF6 (1), [RuII(MeMPTP)(dmbpy)Cl]PF6 (2), [RuII(MeMPTP)(dmcbpy)Cl]PF6 (3) and [RuII(MeMPTP)(Pic)2Cl]PF6 (4) [where, MeMPTP = 4′-(4-methylmercaptophenyl)-2,2′:6′2′′-terpyridine, bpy = 2,2′-bipyridine, dmbpy = 4,4′-dimethyl-2,2′-bipyridine, dmcbpy = 4,4′-dimethoxycarbonyl-2,2′-bipyridine and pic = 4-picoline] were synthesized and characterized via various spectroscopic techniques. The molecular structures of the complexes 1 and 2 were determined by single crystal X-ray diffraction analysis. Catalytic activity for chemical oxidation of water of the complexes 1–4 reveals that the rate of O2 evolution follows the trend 1 > 4 > 2 > 3. Except the unsubstituted complex 1, the catalytic rate for O2 generation of 2 and 4, containing electron-donating (–CH3) groups, is higher than that of 3, bearing an electron-withdrawing (–COOMe) group on the bpy, while the turn over number (TON) of the complexes follows an opposite trend. The difference in the water oxidation activity of the complexes has been correlated to the effect of the substituents on the ancillary ligands in facilitating the electron density on the Ru(II) center to achieve the higher oxidation states required for the water oxidation catalysis. Interestingly, water oxidation study of the complexes 1–4 fills the missing gap between the well-studied mononuclear ruthenium complexes based on terpy/bpy and the MeMPTP/phen ligands.

Palladium(II)/N-Heterocyclic Carbene Catalyzed One-Pot Sequential α-Arylation/Alkylation: Access to 3,3-Disubstituted Oxindoles

Rationally designed fluorene-based mono- and bimetallic Pd-PEPPSI complexes were synthesized and demonstrated to be effective for the one-pot sequential α-arylation/alkylation of oxindoles. This streamlined approach offers efficient access to functionalized 3,3-disubstituted oxindoles in excellent yields (up to 89%) under mild reaction conditions.

'Philic'–'phobic' plate-shaped crystals of aspirin form I

Sneha Sheokand1, Tanshu Jain1, Sameer R Modi1, Bharat Ugale2, Ram Naresh Yadav3, C.M. Nagaraja2, Navin Kumar3, Arvind Kumar Bansal1 1Department Of Pharmaceutics, National Institute Of Pharmaceutical Education And, Mohali, India, 2Department of Chemistry, Indian Institute of Technology (IIT), Ropar, India, 3Department of Mechanical Engineering, Indian Institute of Technology (IIT), Ropar, India E-mail: snehaniper12@gmail.com

Interpenetrated metal–organic frameworks (MOFs) and their applications

Metal–organic frameworks (MOFs) or coordination polymers are highly porous and crystalline inorganic-organic hybrid materials generally consisting of two building elements: inorganic coupling units or metal containing clusters (SBUs) and organic ligands or linkers [1]. These frameworks offer an enormous porosity, which can be used to store large amounts of gases and also the possibility of tailoring the pore size and functionality of MOFs makes them useful materials for carrying out heterogeneous catalytic reactions. The huge sizes of the pores inside MOFs, however, also give rise to a fundamental complication, namely the formation of sublattices occupying the same space.[2] Interpenetration in metal–organic frameworks (MOFs) is an intriguing phenomenon with significant impacts on the structure, porous nature, and functional applications of MOFs which reduces the pore size and the available space within the MOF structure for selective catalytic applications.[3] In our efforts to construct MOFs for heterogeneous catalytic applications and selective gas adsorption, we have synthesized several new interpenetrated porous metal-organic frameworks which have shown interesting catalytic properties and selective CO2 adsorption. The synthesis, structure and catalytic properties of these MOFs will be presented.