Regioselective Deiodination of Iodothyronamines, Endogenous Thyroid Hormone Derivatives, by Deiodinase Mimics

Iodothyronine deiodinases (IDs) are mammalian selenoenzymes that play an important role in the activation and inactivation pound of thyroid hormones. It is known that iodothyronamines (TnAMs), produced by the decarboxylation of thyroid hormones, act as substrates for deiodinases. To understand whether decarboxylation alters the rate and/or regioselectivity of deiodination by using synthetic deiodinase mimics, we studied the deiodination of different iodothyronamines. The triiodo derivative 3,3',5-triiodothyronamine (T3AM) is deiodinated at the inner ring by naphthyl-based deiodinase mimics, which is similar to the deiodination of 3,3',5-triiodothyronine (T3). However, T3AM under-goes much slower deiodination than T3. Detailed experimental and theoretical investigations suggest that T3AM forms a weaker halogen bond with selenium donors than T3. Kinetic studies and single-crystal X-ray structures of T3 and T3AM reveal that intermolecular I center dot center dot center dot I interactions may play an important role in deiodination. The formation of hydrogen- and halogen-bonding assemblies, which leads to the formation of a dimeric species of T3 in solution, facilitates the interactions between the selenium and iodine atoms. In contrast, T3AM, which does not have I center dot center dot I interactions, undergoes much slower deiodination.

Polymorphism in cocrystals of urea:4,4 `-bipyridine and salicylic acid:4,4 `-bipyridine

Polymorphic cocrystals of urea:4,4'-bipyridine and salicylic acid: 4,4'-bipyridine were obtained by crystallization from different solvents. The urea tape is a rare phenomenon in cocrystals but it is consistent in urea:4,4'-bipyridine polymorphic cocrystals. The polymorph obtained from MeCN has symmetrical N-H...N hydrogen bond distances on either side of the urea tape. However, the other form obtained from MeOH has unsymmetrical N-H...N hydrogen bond lengths. In the polymorphic cocrystals of salicylic acid:4,4'-bipyridine, the basic supramolecular synthon acid-pyridine is the same but the 3D packing is different. Both the polymorphic pairs of cocrystals come under the category of packing polymorphs. All polymorphs were characterized by single-crystal X-ray diffraction (SCXRD), PXRD, DSC, FT-IR and HSM. N-H...N and the acid-pyridine supramolecular synthons were insulated by FT-IR vibrational spectroscopy.

Multicomponent Assembly of Fluorescent-Tag Functionalized Ligands in Metal-Organic Frameworks for Sensing Explosives

Detection of trace amounts of explosive materials is significantly important for security concerns and pollution control. Four multicomponent metal organic frameworks (MOFs-12, 13, 23, and 123) have been synthesized by employing ligands embedded with fluorescent tags. The multicomponent assembly of the ligands was utilized to acquire a diverse electronic behavior of the MOFs and the fluorescent tags were strategically chosen to enhance the electron density in the MOFs. The phase purity of the MOFs was established by PXRD, NMR spectroscopy, and finally by singlecrystal XRD. Single-crystal structures of the MOFs-12 and 13 showed the formation of three-dimensional porous networks with the aromatic tags projecting inwardly into the pores. These electron-rich MOFs were utilized for detection of ex- plosive nitroaromatic compounds (NACs) through fluorescence quenching with high selectivity and sensitivity. The rate of fluorescence quenching for all the MOFs follows the order of electron deficiency of the NACs. We also showed the detection of picric acid (PA) by luminescent MOFs is not always reliable and can be misleading. This attracts our attention to explore these MOFs for sensing picryl chloride (PC), which is as explosive as picric acid and used widely to prepare more stable explosives like 2,4,6-trinitroaniline from PA. Moreover, the recyclability and sensitivity studies indicated that these MOFs can be reused several times with parts per billion (ppb) levels of sensitivity towards PC and 2,4,6-trinitrotoluene (TNT).

Polymorphism and Phase Transformation Behavior of Solid Forms of 4-Amino-3,5-dinitrobenzamide

We report the preparation, analysis, and phase transformation behavior of polymorphs and the hydrate of 4-amino-3,5-dinitrobenzamide. The compound crystallizes in four different polymorphic forms, Form I (monoclinic, P2(1)/n), Form II (orthorhombic, Pbca), Form III (monoclinic, P2(1)/c), and Form IV (monoclinic, P2(1)/c). Interestingly, a hydrate (triclinic, P (1) over bar) of the compound is also discovered during the systematic identification of the polymorphs. Analysis of the polymorphs has been investigated using hot stage microscopy, differential scanning calorimetry, in situ variable-temperature powder X-ray diffraction, and single-crystal X-ray diffraction. On heating, all of the solid forms convert into Form I irreversibly, and on further heating, melting is observed. In situ single-crystal X-ray diffraction studies revealed that Form II transforms to Form I above 175 degrees C via single-crystal-to-single-crystal transformation. The hydrate, on heating, undergoes a double phase transition, first to Form III upon losing water in a single-crystal-to-single-crystal fashion and then to a more stable polymorph Form I on further heating. Thermal analysis leads to the conclusion that Form II appears to be the most stable phase at ambient conditions, whereas Form I is more stable at higher temperature.

Depalladation of Neutral Monoalkyne- and Dialkyne-Inserted Palladacycles and Alkyne Insertion/Depalladation Reactions of Cationic Palladacycles Derived from N,N `,N `'-Triarylguanidines as Facile Routes for Guanidine-Containing Heterocycles/Carbocycles: Synthetic, Structural, and Mechanistic Aspects

Depalladation of the monoalkyne-inserted cyclopalldated guanidines (kappa 2(C,N)Pd(2,6-Me2C5H3N)Br] (I and II) in PhCl under reflux conditions and that of the dialkyne-inserted cyclopalladated guanidine kappa(2)(C,N):eta(2)(C=C)PdBr] (III) in pyridine under reflux conditions afforded a guanidine-containing indole (1), imidaziondole (2), and benzazepine (3) in 80%, 67%, and 76%, yields, respectively. trans-L2PdBr2] species (L = 2,6-Me2C5H3N, C5H5N) were also isolated in the aforementioned reactions in 35%, 42%, and 40% yields. Further , the reaction of the cyclopalladated guanidine kappa(2)(C,N)Pd(mu-Br)](2) (IV) with AgBF4 in a CH2Cl2/MeCN mixture afforded the cationic pincer type cyclopalladated guanidine kappa(3)(C,N,O)Pd(MeCN)]BF4] (4) in 85% yield and this palladacycle upon crystallization in MeCN and the reaction of kappa(2)(C,N)Pd(mu-Br)](2) (V) with AgBf(4) in a CH2Cl2/MeCN mixture afforded the cationic palladacycles {kappa(2)(C,N)Pd(MeCN)(2)]BF4](5 and 6) in 89% and 91% yields, respectively. The separate reactions of 4 with 2 equiv of methyl phenylpropiolate (MPP) or diphenylacetylene (DPA) and the reaction of 5 with 2 equiv of MPP in PhCl at 110 degrees C afforded the guanidine-containing quinazolinium tetrafluoroborate 7 in 25-32% yields. The reaction of 6 with 2 equiv of DPA under otherwise identical conditions afforded the unsymmetrically substituted guanidinium tetrafluoroborate 8, containing a highly substituted naphthalene unit, in 82% yield. Compounds 1-8 were characterized by analytical and spectroscopic techniques, and all compounds except 4 were characterized by single-crystal X-ray diffraction. The Molecular structure of 2 and 3 are nove, as the framework in the former arises due to the formation of two C-N bonds upon depalladation while the butadienyl unit in the latter revealed cis,cis stereochemistry, a-feature unprecedented in alkyne insertion chemistry. Plausible pathways for the formation of heterocycles/carbocycles are proposed. the influence of substitutents on the aryl rings fo the cyclopalladated guanidine moiety and those on alkynes upon the nature of the products in addressed. Heterocycles 1 and 7 revealed the presence of two rotamers in about a 1.00:0.43 ratio in CDCl3 and in about a 1.00:0.14 ratio in CD3OD, respectively, as detected by H-1 NMR spectroscopy while in CD3CN and DMSO-d(6) (1) and CD3CN and CDCl3 (7), these heterocycles revealed the presence of a single rotamer. These spectral features are attributed to the restricted C-N single-bond rotation of the CN3 unit of the guanidine moiety, which possibly arises from steric constraint due to the formation of a N-H center dot center dot center dot Cl hydrogen bond with CDCl3 (1) and N-H center dot center dot center dot O and O-D center dot center dot center dot O hydrogen bonds with CD3OD (7).

Phase relations in the system Ca-Ta-O and thermodynamics of calcium tantalates in relation to calciothermic reduction of Ta2O5

Phase equilibria of the system Ca-Ta-O is established by equilibrating eleven samples at 1200 K for prolonged periods and phase identification in quenched samples by optical and scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Four ternary oxides are identified: CaTa4O11, CaTa2O6, Ca2Ta2O7 and Ca4Ta2O9. Isothermal section of the phase diagram is composed using the results. Thermodynamic properties of the ternary oxides are measured in the temperature range from 975 to 1275 K employing solid-state galvanic cells incorporating single crystal CaF2 as the solid electrolyte. The cells essentially measure the chemical potentials of CaO in two-phase fields (Ta2O5 + CaTa4O11), (CaTa4O11 + CaTa2O6), (CaTa2O6 + Ca2Ta2O7), and (Ca2Ta2O7 + Ca4Ta2O9) of the pseudo-binary system CaO-Ta2O5. The standard Gibbs energies of formation of the four ternary oxides from their component binary oxides Ta2O5 and CaO are given by: Delta G(f)((ox))(o) (CaTa4O11) (+/- 482)/J mol(-1) = -58644+21.497 (T/K) Delta G(f)((ox))(o) (CaTa2O6) (+/- 618)/J mol(-1) = -55122+21.893 (T/K) Delta G(f)((ox))(o) (Ca2Ta2O7) (+/- 729)/J mol(-1) = -82562+31.843 (T/K) Delta G(f)((ox))(o) (Ca4Ta2O9) (+/- 955)/J mol(-1) = -126598+48.859 (T/K) The Gibbs energy of formation of the four ternary compounds obtained in this study differs significantly from that reported in the literature. The thermodynamic data and phase diagram are used for understanding the mechanism and kinetics of calciothermic and electrochemical reduction of Ta2O5 to metal. (C) 2014 Elsevier B.V. All rights reserved.

Phenyl carbohydrazone conjugated 2-oxoindoline as a new scaffold that augments the DNA and BSA binding affinity and anti-proliferative activity of a 1,10-phenanthroline based copper(II) complex

A new type of copper(II) complex, CuL(phen)(2)](NO3) (CuIP), where L ((E)-N'-(2-oxoindolin-3-ylidene) benzohydrazide) is a N donor ligand and phen is the N, N-donor heterocyclic 1,10-phenanthroline, has been synthesized. The phenyl carbohydrazone conjugated isatin-based ligand L and CuIP were characterized by elemental analysis, infrared, UV-Vis, H-1 and C-13 NMR and ESI-mass spectral data, as well as single-crystal X-ray diffraction. The interaction of calf thymus DNA (CT DNA) with L and CuIP has been investigated by absorption, fluorescence and viscosity titration methods. The complex CuIP displays better binding affinity than the ligand L. The observed DNA binding constant (K-b = 4.15(+/- 0.18) x 10(5) M-1) and binding site size (s = 0.19), viscosity data together with molecular docking studies of CuIP suggest groove binding and/or a partial intercalative mode of binding to CT DNA. In addition, CuIP shows good binding propensity to the bovine serum albumin (BSA) protein, giving a K-BSA value of 1.25(+/- 0.24) x 10(6) M-1. In addition, the docking studies on DNA and human serum albumin (HSA) CuIP interactions are consistent with the consequence of binding experiments. The in vitro anti-proliferative study establishes the anticancer potency of the CuIP against the human cervical (HeLa) and breast (MCF7) cancer cells; noncancer breast epithelial (MCF10a) cells have also been investigated. CuIP shows better cytotoxicity and sensitivity towards cancer cells over noncancer ones than L under identical conditions, with the appearance of apoptotic bodies. (C) 2014 Elsevier B.V. All rights reserved.

Studying Microstructure in Molecular Crystals With Nanoindentation: Intergrowth Polymorphism in Felodipine

Intergrowth polymorphism refers to the existence of distinct structural domains within a single crystal of a compound. The phenomenon is exhibited by form II of the active pharmaceutical ingredient felodipine, and the associated microstructure is a significant feature of the compound's structural identity. Employing the technique of nanoindentation on form II reveals a bimodal mechanical response on specific single-crystal faces, demonstrating distinct properties for two polymorphic forms within the same crystal.

Optical detection of submicromolar levels of nitro explosives by a submicron sized metal-organic phosphor material

Two isomorphous submicron sized metal-organic network compounds, Y-2(PDA)(3)(H2O)1]center dot 2H(2)O (PDA = 1,4-phenylenediacetate), 1 and Y1.8Tb0.2(PDA)(3)(H2O)1]center dot 2H(2)O, Tb@1 have been synthesized by employing solvent assisted liquid grinding followed by heating at 180 degrees C for 1' min and washing with water. Single crystal X-ray data of bulk 1 confirmed a three dimensional porous structure. The structure and morphology of 1 and Tb@1 were systematically characterized by PXRD, TGA, DSC, IR, SEM and EDX analysis. Dehydrated Tb@1 Tb@1'] shows a high intense visible green emission upon exposure to UV light. The green emission of Tb@1' was used for the detection of nitro explosives, such as 2,4,6-trinitrophenol (TNP), 1,3-dinitro benzene (DNB), 2,4-dinitro toluene (DNT), nitro benzene (NB), and 4-nitro toluene (NT) in acetonitrile. The results show that the emission intensity of dehydrated Tb@1' can be quenched by all the nitro analytes used in the present work. Remarkably, Tb@1' exhibited a high efficiency for TNP, DNB and DNT detection with K-SV K-SV = quenching constant based on linear Stern-Volmer plot] values of 70 920, 44 000 and 35 430 M-1, respectively, which are the highest values amongst known metal-organic materials. Using this material submicromolar level (equivalent to 0.18 ppm), a detection of nitro explosives has been achieved.

Herringbone to cofacial solid state packing via H-bonding in diketopyrrolopyrrole (DPP) based molecular crystals: influence on charge transport

Themono-alkylation of DPP derivatives leads to cofacial pi-pi stacking via H-bonding unlike their di-alkylated counterparts, which exhibit a classical herringbone packing pattern. Single crystal organic field-effect transistor (OFET) measurements reveal a significant enhancement of charge carrier mobility for mono-hexyl DPP derivatives.

Thermoelectric properties of a Mn substituted synthetic tetrahedrite

Tetrahedrite compounds Cu12-xMnxSb4S13 (0 <= x <= 1.8) were prepared by solid state synthesis. A detailed crystal structure analysis of Cu10.6Mn1.4Sb4S13 was performed by single crystal X-ray diffraction (XRD) at 100, 200 and 300 K confirming the noncentrosymmetric structure (space group I (4) over bar 3m) of a tetrahedrite. The large atomic displacement parameter of the Cu2 atoms was described by splitting the 12e site into a partially and randomly occupied 24g site (Cu22) in addition to the regular 12e site (Cu21), suggesting a mix of dynamic and static off-plane Cu2 atom disorder. Rietveld powder XRD pattern and electron probe microanalysis revealed that all the Mn substituted samples showed a single tetrahedrite phase. The electrical resistivity increased with increasing Mn due to substitution of Mn2+ at the Cu1+ site. The positive Seebeck coefficient for all samples indicates that the dominant carriers are holes. Even though the thermal conductivity decreased as a function of increasing Mn, the thermoelectric figure of merit ZT decreased, because the decrease of the power factor is stronger than the decrease of the thermal conductivity. The maximum ZT = 0.76 at 623 K is obtained for Cu12Sb4S13. The coefficient of thermal expansion 13.5 +/- 0.1 x 10(-6) K-1 is obtained in the temperature range from 460 K to 670 K for Cu10.2Mn1.8Sb4S13. The Debye temperature, Theta(D) = 244 K for Cu10.2Mn1.8Sb4S13, was estimated from an evaluation of the elastic properties. The effective paramagnetic moment 7.45 mu(B)/f.u. for Cu10.2Mn1.8Sb4S13 is fairly consistent with a high spin 3d(5) ground state of Mn.

Sunlight-Induced Covalent Marriage of Two Triply Interlocked Pd-6 Cages and Their Facile Thermal Separation

A template-free triply interlocked Pd-6 cage (2) was synthesized by two-component self-assembly of cis-blocked 90 degrees acceptor cis-(tmen)Pd(NO3)(2) (M) and 1,3,5-tris((E)-2-(pyridin-3-yl)vinyl)benzene (L). Assembly 2 was characterized by H-1 NMR and ESI-MS, and the structure was confirmed by X-ray crystallography, which revealed a parallel conformation of the olefin double bonds belonging to the adjacent cages in the solid state at a distance of 3.656 angstrom, thereby indicating the feasibility of 2+2] photochemical reaction. Two adjacent interlocked cages were covalently married together by intermolecular 2+2] cycloaddition in a single crystal-to-single crystal fashion upon exposure to sunlight/UV irradiation. Most surprisingly, the covalently married pair was easily separated thermally in aqueous medium under mild reaction conditions.

Synthesis, molecular docking and anti-mycobacterial evaluation of new imidazo1,2-a]pyridine-2-carboxamide derivatives

New anti-tubercular agents, imidazo1,2-a]pyridine-2-carboxamide derivatives (5a-q) have been designed and synthesized. The structural considerations of the designed molecules were further supported by the docking study with a long-chain enoyl-acyl carrier protein reductase (InhA). The chemical structures of the new compounds were characterized by IR, H-1 NMR, C-13 NMR, HRMS and elemental analysis. In addition, single crystal X-ray diffraction has also been recorded for compound 5f. Compounds were evaluated in vitro against Mycobacterium tuberculosis H37Rv, and cytotoxicity against HEK-293T cell line. Amongst the tested compounds 5j, 5l and 5q were emerged as good anti-tubercular agents with low cytotoxicity. The structure-anti TB activity relationship of these derivatives was explained by molecular docking. (C) 2014 Elsevier Masson SAS. All rights reserved.

Synthesis and antioxidant activity study of pyrazoline carrying an arylfuran/arylthiophene moiety

A novel series of N-acetyl-3-aryl-5-(5-(p/o-nitrophenyl)-2-furyl//thienyl)-substituted pyrazolines (3a-o) were synthesized by the reaction of 1-aryl-3-(5-(p/o-nitrophenyl)-2-furyl/thienyl)-2-propene-1-ones with hydrazine hydrate in acetic acid medium. The structures of the newly synthesized compounds were established by IR, H-1-NMR, mass spectra and a single-crystal X-ray study. The antioxidant activities of the synthesized compounds were determined using the DPPH scavenging assay. The compounds 3a, 3f, 3h and 3o showed moderate activity.

Modulation of Electronic and Self-Assembly Properties of a Donor-Acceptor-Donor-Based Molecular Materials via Atomistic Approach

The performance of molecular materials in optoelectronic devices critically depends upon their electronic properties and solid-state structure. In this report, we have synthesized sulfur and selenium based (T4BT and T4BSe) donor-acceptor-donor (D-A-D) organic derivatives in order to understand the structure-property correlation in organic semiconductors by selectively tuning the chalcogen atom. The photophysical properties exhibit a significant alteration upon varying a single atom in the molecular structure. A joint theoretical and experimental investigation suggests that replacing sulfur with selenium significantly reduces the band gap and molar absorption coefficient because of lower electronegativity and ionization potential of selenium. Single-crystal X-ray diffraction analysis showed differences in their solid-state packing and intermolecular interactions. Subsequently, difference in the solid-state packing results variation in self-assembly. Micorstructural changes within these materials are correlated to their electrical resistance variation, investigated by conducting probe atomic force microscopy (CP-AFM) measurements. These results provide useful guidelines to understand the fundamental properties of D-A-D materials prepared by atomistic modulation.