Crystal structures of 3/4-pyridyl-based thiosemicarbazones and related Cu and Ni coordination compounds

In this investigation, the crystal structures of the thio-ligands 3-formylpyridine 4-phenylthiosemicarbazone (C₁₃H₁₂N₄S, 1 ) and 4-benzoylpyridine 4-ethylthiosemicarbazone (C₁₅H₁₆N₄S, 2 ), and of two new coordination compounds, chlorido(3-formylpyridine 4-phenylthiosemicarbazone-κS)bis(triphenylphosphane-κP)copper(I) acetonitrile monosolvate, [CuCl(C₁₃H₁₂N₄S)(C₁₈H₁₅P)₂]·CH₃CN, 3 , and bis(3-formylpyridine 4-ethylthiosemicarbazonato-κ²N¹,S)nickel(II), [Ni(C₉H₁₁N₄S)₂], 4 , are reported. In complex 3 , the thio-ligand coordinates in a neutral form to the Cu atom through its S-donor atom, and in complex 4 , the anionic thio-ligand chelates to the Ni atom through N- and S-donor atoms. The geometry of complex 3 is distorted tetrahedral [bond angles 99.70 (5)–123.23 (5)°], with the P—Cu—P bond angle being the largest, while that of complex 4 is square planar, with trans-S—Ni—S and N—Ni—N bond angles of 180°.     

Efficient Elemental Iodine Catalyzed One-Pot Synthesis of 2,4,5-Triarylimidazoles

Summary. Elemental iodine is used as an efficient catalyst for the synthesis of 2,4,5-triarylimidazoles in excellent yields via condensation of benzoin, ammonium acetate, and aromatic aldehydes. This is a simple, one-pot, high yielding technique using cheap, non-toxic iodine in catalytic amounts.     

Electronic structure of Ni2TiAl: Theoretical aspects and Compton scattering measurement

In this paper, we report electron momentum density of Ni₂TiAl alloy using an in-house 20 Ci ¹³⁷Cs (661.65 keV) Compton spectrometer. The experimental data have been analyzed in terms of energy bands and density of states computed using linear combination of atomic orbitals (LCAO) method. In the LCAO computations, we have considered local density approximation, generalized gradient approximation and recently developed second order generalized gradient approximation within the frame work of density functional theory. Anisotropies in theoretical Compton profiles along [1 0 0], [1 1 0] and [1 1 1] directions are also explained in terms of energy bands.     

Efficient Elemental Iodine Catalyzed One-Pot Synthesis of 2,4,5-Triarylimidazoles

Elemental iodine is used as an efficient catalyst for the synthesis of 2,4,5-triarylimidazoles in excellent yields via condensation of benzoin, ammonium acetate, and aromatic aldehydes. This is a simple, one-pot, high yielding technique using cheap, non-toxic iodine in catalytic amounts.     

The Effect of a Hydrogen Bonding Environment (Dimethyl Sulfoxide) on the Ionisation and Redox Properties of the Thiol Group in Cysteine and a Protein Disulfide Isomerase Mimic (Vectrase)

Increasing enrichment of dimethyl sulfoxide, DMSO, in DMSO-water mixtures causes a reversal in the thermodynamic dissociation constants, pK _as, and has a marked effect on the redox potentails of the thiolic and amino groups in cysteine and the protein disulfide isomerase (PDI) mimic BMC, Vectrase. This paper illustrates the effect of a hydrogen-bonding environment on the ionisation and redox properties of thiol groups in amino acids. A combination of potentiometry and Raman spectroscopy was applied to rationalise the observations. Intracellular environments are full of hydrophobic, hydrogen-bonding environments. The results illustrate the profound effects of the local environment on the thiol group.     

Mitigating repulsions in close quarters: Copper tells us how!

Four copper(I) complexes of short bite ligands, bis(diphenylphosphino)amine (dppa) and bis(diphenylphosphino)isopropylamine (dppipa) were synthesized from appropriate precursors. All complexes were characterized by single crystal X-ray crystallography and spectroscopic techniques. In each of these complexes, two filled shell cations are forced into close proximity (≈2.7–2.8 Å). With no strong π acid ligands to siphon electron density from the filled d shell, the unavoidable repulsive d¹⁰–d¹⁰ interaction is mitigated when an unsymmetrical coordination environment around the copper atoms exists. The coordinatively saturated copper ion functions as a donor to the coordinatively unsaturated copper. A Cambridge Structural Database (CSD) search reveals the greater propensity of clusters with short contacts to adopt unsymmetrical coordination.     

Theoretical study of the effect of radiation on thymine

The possible effects of radiation exposure to DNA are studied by investigations for the thymine residue. Detailed analysis of the various addition and other products is undertaken theoretically, using the semiempirical AM1 procedure. The results agree with the experimental finding that the loss of hydrogen on radiation exposure occurs from the C₅-methyl group and hydroxyl radical addition occurs at C₆, yielding the ‘5-yl’ radical. This radical is nonplanar, the axial conformer being slightly preferred over the equatorial one. In contrast, the other possible radical, the ‘6-yl’ radical, is almost planar. These results are important in understanding the conformational changes in DNA as a consequence of radiation exposure.     

Copper(I) Derivative of Pyridine-3-carbaldehyde-N-ethylthiosemicarbazone and Triphenylphosphine—First Case of Crystal Structure Study

The synthesis and crystal structure of pyridine-3-carbaldehyde-N-ethylthiosemicarbazone (3-pytscH-NHEt) 1, and its Cu^I complex of stoichiometry, [CuCl(3-pytscH-NHEt)(PPh₃)₂] 2, studied using single crystal X-ray crystallography, are reported in this paper. Crystal data: 1, monoclinic, P2₁/n, a?=?6.6322(3), b?=?21.1200(8), c?=?7.2989(3) Å; β?=?91.883(4), T?=?173(2), R factor?=?0.0457; 2: triclinic, P-1, a?=?19.3600(5), b?=?20.6241(6), c?=?23.8015(6) Å,α?=?92.647(2), β?=?104.388(2), γ?=?114.377(3), R factor?=?0.0662. The thio-ligand, as a neutral entity, is coordinating to Cu through its S donor atom in complex 2. It has exhibited an unusual feature of forming four independent molecules (A, B, C, D) in the unit cell, with minor differences in the bond angles / distances / torsion angles. The geometry of each molecule of 2 is distorted tetrahedral. Crystal packing, as well as Infrared, electronic absorption and proton NMR spectroscopic studies, are also reported. Copper compound 2 represents the first example of a structurally studied copper coordination compound of 3-pyridyl based thiosemicarbazones.

Graphical Abstract

Copper(I) chloride with pyridine-3-carbaldehyde-N-ethylthiosemicarbazone and PPh₃ in CH₃CN yielded a copper compound, 2 (Green-Cl, blue-N; aqua-Cu, orange-S, magneta-P).

     

Ultrasensitive Organic Humidity Sensor with High Specificity for Healthcare Applications

Humidity sensors have gained immense importance as non‐invasive, wearable healthcare devices for personal care as well as disease diagnostics. However, non‐specificity, poor stability at extreme conditions, and low sensitivity of the humidity sensor inhibit its usage as a health monitoring device. In the present study, N?F containing organic molecule, Selectfluor^TM (F‐TEDA) based humidity sensors with ～1–2 mm long needle‐shaped crystals is fabricated on interdigitated electrodes resulting in excellent performance. The unidirectional growth of crystals led to the formation of a conduction pathway for water molecules across the crystal, which otherwise are non‐conducting. The as‐fabricated humidity sensor at an operational voltage of 0.8 V displays a sensitivity of six orders in magnitude, best reported so far. The sensor does not exhibit any response upon exposure to various volatile organic compounds and reactive gases, indicating remarkable specificity. The sensor is tolerant to high moisture of 95 % for prolonged hours followed by monitoring over several days and degrades to 50 % of its original sensitivity only after continuous exposure for several days. Electrochemical impedance spectroscopy (EIS) shows reversal from resistive to capacitive behavior with increasing humidity levels. The fabricated humidity sensor acts as a healthcare device for breath rate monitoring and touch‐free examination of skin moisture.