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1.
Steinar Husebye Dima Mughannam Karl W. Törnroos 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1825-1837
The complexes were synthesised by adding a hot solution of the appropriate substituted thiourea in MeOH (Br m complexes) or DMF (I m complexes) to a solution of TeO 2 dissolved in hot conc. HCl. The structures of the resulting four-coordinate square planar complexes, cis -[TeBr 2 {( i PrNH) 2 CS} 2 ] ( 1 ), cis -[TeBr 2 {( i BuNH) 2 CS} 2 ] ( 2 ), trans -[TeI 2 {( i PrNH) 2 CS} 2 ] ( 3 ), and trans -[TeI 2 {( i BuNH) 2 CS} 2 ] ( 4 ), were studied by means of X-ray crystallographic methods. The average Te-S bond length in 1 and 2 is 2.5364 Å. The corresponding average Te-Br bond length is 2.9639 Å, reflecting the stronger trans influences of the two thioureas as compared to that of bromide. In 3 and 4 where there is no trans influence affecting the Te-ligand bonds, the average Te-S and Te-I bond lengths are 2.6926 and 2.9761 Å respectively. Tetraalkyl- or arylsubstituted thioureas alone as well as bulky disubstituted thioureas together with I m ligands seem to favor formation of trans complexes. 相似文献
2.
Wenbo Dong Zhiying Qin Kuixing Wang Yueyuan Xiao Xiangyang Liu Shijie Ren Longyu Li 《Angewandte Chemie (International ed. in English)》2023,62(5):e202216073
Imine-linked covalent organic frameworks (COFs) have been extensively studied in photocatalysis because of their easy synthesis and excellent crystallinity. The effect of imine-bond orientation on the photocatalytic properties of COFs, however, is still rarely studied. Herein, we report two novel COFs with different orientations of imine bonds using oligo(phenylenevinylene) moieties. The COFs showed similar structures but great differences in their photoelectric properties. COF-932 demonstrated a superior hydrogen evolution performance compared to COF-923 when triethanolamine was used as the sacrificial agent. Interestingly, the use of ascorbic acid led to the protonation of the COFs, further altering the direction of electron transfer. The photocatalytic performances were increased to 23.4 and 0.73 mmol g−1 h−1 for protonated COF-923 and COF-932, respectively. This study provides a clear strategy for the design of imine-linked COF-based photocatalysts and advances the development of COFs. 相似文献
3.
Isomerism of atomically precise noble metal nanoclusters provides an excellent platform to investigate the structure–property correlations of metal nanomaterials. In this study, we performed density functional theory (DFT) and time‐dependent (TD‐DFT) calculations on two Au21(SR)15 nanoclusters, one with a hexagonal closed packed core (denoted as Au21 hcp ), and the other one with a face‐centered cubic core (denoted as Au21 fcc ). The structural and electronic analysis on the typical Au–Au and Au–S bond distances, bond orders, composition of the frontier orbitals and the origin of optical absorptions shed light on the inherent correlations between these two clusters. 相似文献
4.
Dipole polarizability,structure, and stability of [2+2]-linked fullerene nanostructures (C60)n (n≤7)
In the present work, structural features, dipole polarizability, and stability of two most promising oligomeric series (C60)n with zigzag and linear arrangement of the fullerene cages have been studied by the PBE/3ζ density functional theory method. Their mean polarizabilities and polarizability exaltations are linearly correlated with the molecular size (maximal intercage distance). Linear (C60)n have higher polarizability than zigzag oligomers with the same n. Based on the example of hexamers (C60)6, we have shown that connectivity (number of connections) has no effect on the resulting polarizability but maximal remoteness does, i.e. the geometric factor is more decisive for mean polarizability of such fullerene nanostructures. Stability of (C60)n decreases with growing molecular size for linear structures and slowly increases in the case of zigzag (C60)n. The found dependences of polarizability and stability on the molecular size may be used for assessing these parameters of larger fullerene nanostructures, hardly computable with quantum chemical methods. 相似文献
5.
《Journal of Coordination Chemistry》2012,65(21):2335-2342
The ruthenium tricarbonyl derivative [Ru(CO)3(sha)] (1), was synthesized from reaction of [Ru3(CO)12] with N-salicylidene-2-hydroxyaniline (shaH2) Schiff base. The corresponding reactions of the ruthenium cluster with shaH2 in presence of a secondary ligand L,L?=?pyridine and triphenyl phosphine resulted in the formation of the dicarbonyl derivatives [Ru(CO)2(shaH2)(L)] (2, 3). In the presence of L?=?2-aminobenzimidazole or thiourea, two complexes [Ru(CO)2(sha)(L)] (4, 5) were formed and the shaH2 ligand bonded to ruthenium oxidatively. The bipyridine(bpy) derivative had the molecular formula [Ru(CO)2(shaH)(bpy)] (6), with shaH coordinated bidentate. All complexes were characterized by elemental analysis and mass, IR, 1H NMR and UV–Vis spectroscopy. The spectroscopic studies of these complexes revealed several structural arrangements and different tautomeric forms. 相似文献
6.
《Journal of Coordination Chemistry》2012,65(16):1835-1846
The crystal structures of [Mn(bpa)2](ClO4)2 (1), [bpa?=?bis(2-pyridylmethyl)amine], and Mn(6-Mebpa)2(ClO4)2 (2), [6-Mebpa?=?(6-methyl-2-pyridylmethyl)(2-pyridylmethyl)amine] have been determined. In 1, two facial [Mn(bpa)2]2+ isomers are observed in the same unit cell, one with C i (1a) and the other with C2 (1b) symmetries. In 2, only the isomer with C2 symmetry is observed. The structure of [Mn(bpa)2]2+ with only C2 symmetry has been reported previously (Inorg. Chem., 31, 4611 (1992)). The bond length order Mn–Namine?>?Mn–Npyridyl, observed in the C2 and the C i isomers in the crystals of 1, is the reverse of the order observed in the structure of [Mn(bpa)2](ClO4)2 which contains only the C2 isomer in the unit cell. The structure of 2 in which only the C2 isomer is found, also shows the bond length order Mn–Npyridyl?>?Mn–Namine. In cyclic voltammetric experiments in acetonitrile solutions, 1 and 2 show irreversible anodic peaks at E p?=?1.60 and 1.90?V respectively, (vs. Ag/AgCl), assigned to the oxidation of Mn(II) to Mn(III). The substantially higher oxidation potential of 2 is attributable to a higher rearrangement energy in complex 2 due to the steric effect of the methyl substituent. 相似文献
7.
Two novel isopropylamine‐templated uranyl chromates, [(CH3)2CHNH3]3[(UO2)3(CrO4)2O(OH)3] ( 1 ) and [(CH3)2CHNH3]2[(UO2)2(CrO4)3(H2O)] ( 2 ) were prepared by hydrothermal method at 100 °C. The compounds were characterized by electron microprobe analysis and X‐ray diffraction crystal structure analysis [ 1 : trigonal, P31m, a = 9.646(4), c = 8.469(4) Å, V = 682.4(5) Å3; 2 : monoclinic, P21/c, a = 11.309(3), b = 11.465(3), c = 17.055(5) Å, β = 99.150(6)°, V = 2183.2(11) Å3]. The structure of 1 is based upon trimers of uranyl bipyramids interlinked by CrO4 tetrahedra to form [(UO2)3(CrO4)2O(OH)3]3– layers, whereas, in the structure of 2 , UO7 and UO6(H2O) pentagonal bipyramids are linked through CrO4 tetrahedra into the [(UO2)2(CrO4)3(H2O)]2– layers. The structures show many similarities to related uranyl selenate compounds, thus providing additional data on similarities and differences between uranyl sulfates, chromates, selenates, and molybdates. 相似文献
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9.
Deepika Kathuria Sumit S. Chourasiya Sanjay K. Mandal Asit K. Chakraborti Uwe Beifuss Prasad V. Bharatam 《Tetrahedron》2018,74(23):2857-2864
Treatment of 1,3-diaryl-propene-2-one with aminoguanidine under acidic conditions for a short reaction period (1?h) delivers - in accordance with a literature report - the corresponding guanylhydrazones. However, when the reaction time was increased to 12?h, formation of the ring annulated product 4,5-dihydro-1H-pyrazole-1-carboximidamide was observed. This is the first case of ring-chain isomerism in conjugated guanylhydrazones. The acyclic conjugated guanylhydrazone and the corresponding annulated product (4,5-dihydro-1H-pyrazole-1-carboximidamide) could be clearly distinguished by means of UV and NMR spectroscopy. The formation of the ring isomer was further confirmed by single crystal XRD analysis. The time-dependent 1H NMR study indicated the gradual transformation of the open-chain compound into the cyclic one. The mechanistic insights into the formation of these two products were explored using quantum chemical methods which revealed that the ring isomer is thermodynamically more stable than the open-chain isomer by 6–11?kcal/mol and the barrier for cyclization was found to be 31.37?kcal/mol. 相似文献
10.
The spectral and photophysical properties of the betacarboline anhydrobase, N2-methyl-9H-pyrido[3,4-b]indole, BCA, have been studied in aprotic solvents. The influence of solvent polarity and hydrogen-bonding interactions on the absorption, steady-state and time-resolved fluorescence spectra provides founded proofs on the existence of two ground state BCA isomers whose equilibrium concentrations change with the medium polarity. We propose that the isomers possess quinonoid, Q, and dipolar zwitterionic, Z, structures, respectively. Upon excitation, each isomer gives rise to a double emission. To account for this phenomenon, photophysical diagrams based on the simultaneous emission from locally excited states, LE, and charge transfer excited states, CT, are proposed. 相似文献