Bis (1, 3, 5-triazinane-2, 4, 6-trione) 1, 4-diazabicyclo [2.2.2] octane (TTDO) an adduct or co-crystallization product was prepared from 1, 4-Diazabicyclo [2·2·2] octane (DABCO) and cyanuric acid (CA) by solvent evaporation method. The TTDO molecule crystallized in the centrosymmetric space group C2/c with a monoclinic crystal system. The structure has an interaction between N(CA)-H and DABCO-N. The DABCO comes in between two CA moieties linearly disposed on either side of the two nitrogen atoms of DABCO. On sidewise, the CA molecules shows extended H-bonding showing a supramolecular assembly as compelled by the disposition of the groups. The Hirshfeld surface analyses showed the extent of intermolecular interactions in the adduct molecule. The FT-IR confirmed the presence of N–H, C–H, C = O and CN stretching vibrations of the molecule. The photoluminescence spectra showed an intense peak at 532 nm in the green region. TG-DTA analyses showed that the molecule is stable up to 143 °C and loses CA in the first stage and DABCO decomposes subsequently. TTDO inhibits Gram-positive (Staphylococcus aureus) and Gram-negative (Salmonella typhi) bacteria.
A new trans-bidentate ligand, 1,2-bis(quinolin-2-ylethynyl)benzene, was synthesized and coordinated to PdCl2. The structure of the acetonitrile solvate of this species was determined by single-crystal X-ray diffraction. The complex crystallizes in the orthorhombic space group Ibam, with a = 25.0726(18) Å, b = 11.7373(6) Å, and c = 18.9700(10) Å in a layered structure. When bound to 1,2-bis(quinolin-2-ylethynyl)benzene, the Pd(II) metal center displays a distorted square planar geometry. This coordination complex was compared to PdCl2-coordinated 1,2-bis(2-pyridylethynyl)benzene, a previously reported trans-bidentate ligand. Structural comparison indicated that the binding pocket for these two trans-bidentate ligands are similar, though the 1,2-bis(quinolin-2-ylethynyl)benzene ligand is somewhat more planar.
A new trans-bidentate ligand, 1,2-bis(quinolin-2-ylethynyl)benzene (BQEB), was synthesized and coordinated to PdCl2.
The molecular environments in the crystal of two dibenzoylnaphthalene derivatives, having similar molecular formulas with a difference of only one substituent, that is, a 2-hydroxy group and 2-ethoxy group, were comparatively investigated with respect to the types of weak interactions, using an X-ray crystal structural study reinforced by Hirshfeld surface analysis and two-dimensional plotting of the normalised interatomic distance crossing the molecular surface. The general X-ray crystal structural analysis determined effective non-covalent bonding intra/intermolecular interactions to be the governing interactions for molecular packing based short interatomic distances. The minute spatial structure around respective interactions demonstrates the characteristics of non-covalent bonding interatomic interactions. The general X-ray crystal structural analysis further revealed the relationship between the entire crystalline symmetricity and the fashion of the interactions. Hirshfeld surface analysis revealed the location of the short contacts on the molecular surface. Two-dimensional plotting exhibited the contribution of the interacting atomic pairs covering the molecular surfaces as the geometrical distribution of the effective intermolecular non-covalent bonding interactions. The differences in the determined packing features and proximity of the two compounds were rationally interpreted according to the strength categorisation of the non-covalent bonding interactions especially in relation to the proportional/disproportional distribution of the molecular contact index. The comparison illustrated that the superior intermolecular interaction concentrates on the short interatomic distances and strain at the specified region of the molecular aggregate, resulting in adequate flexibility of the extroverted sides to achieve highly symmetrical interactions.
Ethoxy–hydroxy diaroylnaphthalene compound forms cyclic classical hydrogen bond-based dimeric aggregate bearing four C–H‧‧‧O non-classical hydrogen bonds in the core region and four effective π‧‧‧π stackings around the extroverted zone, whereas ethoxy–ethoxy homologous compound shows π‧‧‧π stacking based dimeric aggregate having four C–H‧‧‧O non-classical hydrogen bonds around the extroverted zone.
Two new bis(β-diketone) ligands based on triphenylamine have been prepared and crystallized. Treatment of 4,4′-diformyltriphenylamine with two phospholenes (2,2,2-trimethoxy-4,5-dimethyl-1,3,2-dioxaphospholene and 2,2,2-trimethoxy-4,5-diethyl-1,3,2-dioxaphospholene) afforded the bis(β-diketones) triphenylaminebis(2,4-pentanedione) (tpbaH2, 1); and triphenylaminebis(3,5-heptanedione) (tpbprH2, 2) as white solids. X-ray analysis of 1 and 2 shows that they are in the enol form. Also, their triphenylamine moieties have a chiral “propeller” shape; the centrosymmetric structures contain equal numbers of the two enantiomeric propellers. Reaction of 1 and 2 with [Cu(NH3)4]2+(aq) yielded dark-green solids. The Cu complex of 1 was insoluble in common solvents, but that of 2, Cu4(tpbpr)4 (3), is soluble in dichloromethane and chloroform. 3 is assigned the cyclic tetrameric structure Cu4(tpbpr)4 based on ESI–MS and microanalytical data. This is similar to the copper(II) β-diketonate molecular squares reported previously from our group. Molecular modeling indicates that Cu4(tpbpr)4 has Cu···Cu distances of ca. 21 Å, as compared to ca. 14 Å in the previous molecular squares.
Crystal structures of two new bis(β-diketones) are reported, which are likely to form large supramolecular structures on reaction with metal ions such as Cu2+.
Three crystalline forms of nicotinamide riboside chloride (NR-Cl), namely Form A, Form B and Form C, were prepared and characterized. Form A and Form B are true polymorphs of anhydrous forms, while Form C is a pseudo-polymorph of a methanolate solvate form. The relative polymorphic stability relationship among these three crystalline forms was established, and Form B was found to be the most stable form with a higher crystal density (1.591 Mg/m3) and a higher melting/decomposing temperature (123 °C) compared to that of Form A (1.512 Mg/m3 and 119 °C). The crystal structure of Form B (orthorhombic P212121 space group, a = 7.0008(11) Å, b = 9.6465(15) Å, c = 17.971(3) Å, V = 1213.7(3) Å3, Z = 4) was determined by single crystal X-ray diffraction analysis.
The crystal structure of the most stable polymorph of nicotinamide riboside chloride (NR-Cl) is reported.
The more polar product of the Michael addition of 4-hydroxycoumarin to mesityl oxide, an analog of warfarin, crystallizes as the racemic cyclic coumarin hemiketal 2-hydroxy-2,4,4-trimethyl-3,4-dihydro-2H,5H-pyrano[3,2-c][1] benzopyran-5-one. Crystals occur in the monoclinic system, space group P2(1)/n, with a 6.6655(4)Å, b 12.9450(7)Å, c 14.5809(7)Å, β 97.909(5)°, Z = 4. In solution by nuclear magnetic resonance (400 MHz), a dynamic equilibrium exists between the enantiomeric coumarin hemiketals through an unobserved intermediate open tautomer. Diastereomeric methylene and methyl Hs exchange slowly in non-polar solvents (acetic acid and chloroform), much faster in polar, aprotic solvents (acetone and dimethylsulfoxide). In methanol, dynamic behavior begins in the slow-exchange region at 288–310 K, with signal coalescence at 310.5 K, followed by fast-exchange behavior. The barrier to cyclic-open-cyclic (racemization) was found to be ΔG‡ = + 63(1) kJ/mol (in CD3OD), with a racemization rate of 30 s−1 at 298 K, 155 s−1 at 310.5 K. Density functional theory (DFT) computations modelling the open and cyclic coumarin tautomers, including solvent fields, confirms that the open-form is 60–70 kJ/mol higher in energy than the cyclic hemiketal. Additionally, modelling supports the contention that chromone tautomers are insignificant participators in solution. An operative gem-dimethyl effect, supported by the proximity of the methyls to the coumarin carboxy oxygen, apparently favors rotamers that bring the side-chain ketone into proximity with the coumarin enolic hydroxy. The less-polar by-product of the Michael addition has been characterized by spectroscopy and crystallography as 2,2,4-trimethyl[2H,5H]pyrano[3,2-c][1]benzopyran-5-one. Computations on the alkyl warfarin analog 2-hydroxy-2,4-dimethyl-3,4-dihydro-2H,5H-pyrano[3,2-c] [1]benzopyran-5-one, lacking the gem-dimethyl effect significantly stabilizes the intermediate open coumarin form, which accords with open-form observations in solution for this analog and for warfarin reported in the literature.
Selenaphosphocine [(–OC6H2(tBu)2(µ-Se)(tBu)2C6H2O–)PhP] (1) on treatment with [Pd(COD)Cl2] yielded P,Se-coordinated complex [{(–OC6H2(tBu)2(µ-Se)(tBu)2C6H2O–)PhP}(PdCl2)] (2), whereas the reaction of 1 with [AuCl⋅SMe2] resulted in only P-coordinated complex [{(–OC6H2(tBu)2(µ-Se)(tBu)2C6H2O–)PhP}(AuCl)] (4). The reaction of 1 with [Rh(CO)2Cl]2 in 4:1 molar ratio yielded a rare RhIII octahedral complex [{PhP(–OC6H2(tBu)2(µ-Se)(tBu)2C6H2O–)}{PPh(–OC6H2(tBu)2)(Se(tBu)2C6H2O–)}(RhCl)] (3) in good yield, in which one of the C–Se bonds of selenophosphocine is added oxidatively to RhI. All of the complexes have been structurally characterized and are crystallized in the triclinic crystal system with P¯1 space group. All complexes showed intermolecular C–H⋯O and C–H ⋯Se hydrogen bonding interactions, that play major role in the crystal packing to form a three-dimensional array. In complex 2, the crystal packing reveals the presence of rare intermolecular Pd⋯Cl interactions. Hirshfeld surface analysis, dnorm and two-dimensional fingerprint plots were investigated to validate the contributions of the different intermolecular contacts within the supramolecular structure. A Hirshfeld surface analysis indicated that the most significant contributions to the crystal packing of 2 are from H⋯H (66.3%), C⋯H/H⋯C (13.5%), Cl⋯H/H⋯Cl (13.7%), Cl⋯C/C⋯Cl (1.8%) and Cl⋯C/C⋯Cl (1.0%) contacts, and those for 3 are from H⋯H (88.3%), C⋯H/H⋯C (8.3%) and Se⋯H/H⋯Se (3.6%) contacts, while those for 4 are from H⋯H (71.5%), C⋯H/H⋯C (9.9%), Cl⋯H/H⋯Cl (10.2%), Se⋯H/H⋯Se (2.7%) and Au⋯H/H⋯Au (1.7%) contacts.
This paper describes the cleavage of a C–Se from dioxaselenaphosphocine and its oxidative addition to rhodium(I) complex and Hirshfeld analysis.
The structures of the isomeric 2,5-dihydrothiophene 1,1-dioxide [orthorhombic, a = 11.340(2), b = 7.0887(15), c = 6.2811(13) Å, space group Pnma] and 2,3-dihydrothiophene 1,1-dioxide [orthorhombic, a = 6.3903(13), b = 7.2783(16), c = 11.075(2) Å, space group Pnma] have been determined and show perfectly planar rings with the expected bond lengths and angles. In contrast, the halogenated derivatives 3,3,4,4-tetrachlorotetrahydrothiophene 1,1-dioxide [monoclinic, a = 11.8716(8), b = 6.5579(4), c = 11.4802(8) Å, β = 97.705(17), space group P21/c] and 2,3-dibromotetrahydrothiophene 1,1-dioxide [orthorhombic, a = 5.2502(3), b = 11.3561(6), c = 24.9802(17) Å, space group Pbca] both show twisted conformations. The degree of planarity is compared with that in the structures of comparable 5-membered ring cyclic sulfones and C–H…O hydrogen bonding patterns are discussed for all four structures.
The two isomeric sulfolenes are perfectly planar while tetrachloro- and dibromo-derivatives adopt twisted structures.
A new heterocyclic ligand, L [4-(1-methylimidazole)-2,6-di(pyrazinyl)pyridine] has been synthesized and characterized by adequate spectroscopic methods. The title ligand (L) was then utilized for synthesizing a new complex, namely, [Cu(L)(NCS)(SCN)]·H2O (complex 1) and crystallographically characterised by single-crystal X-ray analysis. In the solid state, the complex unit is stabilized through various hydrogen bonding interactions along with π···π stacking and lone pair···π interactions that lead the molecules to generate diverse supramolecular architectures. Interestingly, the complex exhibits weak S···S interaction which has significant contribution in the solid state crystal packing. All the intermolecular interactions that are involved within the structure are quantified through Hirshfeld surface analyses and confirmed by Bader’s theory of ‘atoms-in-molecules’ (AIM). Finally, an interaction energy analysis was carried out to study the interactions between pairs of molecules.
The present article reports the synthesis, structural elucidation mentioning the role of supramolecular interactions (π···π stacking, lone pair···π and S···S interactions) and theoretical rationalization [quantified through Hirshfeld surface analyses and confirmed by Bader’s theory of ‘atoms-in-molecules’ (AIM)] of a new dithiocyanato-κ-N, κ-S-copper (II) complex derived from heterocyclic ligand, 4-(1-methylimidazole)-2,6-di(pyrazinyl)pyridine.
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