NiII molecular complex with a tetradentate aminoguanidine-derived Schiff base ligand: structural, spectroscopic and electrochemical studies and photoelectric response

The new molecular nickel(II) complex, namely, {4-bromo-2-[({N′-[(2-oxidobenzylidene)amino]carbamimidoyl}imino)methyl]phenolato}nickel(II) N,N-dimethylformamide solvate monohydrate, [Ni(C15H11BrN4O2)]·C3H7NO·H2O, (I), crystallizes in the triclinic space group P\overline{1} with one molecule per asymmetric unit. The guanidine ligand is a product of Schiff base condensation between aminoguanidine, salicylaldehyde and 5-bromosalicylaldehyde templated by Ni2+ ions. The chelating ligand molecule is deprotonated at the phenol O atoms and coordinates the metal centre through the two azomethine N and two phenolate O atoms in a cis-NiN2O2 square-planar configuration [average(Ni—N/O) = 1.8489 Å, cis angles in the range 83.08 (5)–95.35 (5)°, trans angles of 177.80 (5) and 178.29 (5)°]. The complex molecule adopts an almost planar conformation. In the crystal, a complicated hydrogen-bonded network is formed through N—H...N/O and O—H...O intermolecular interactions. Complex (I) was also characterized by FT–IR and 1H NMR spectroscopy. It undergoes an NiII ↔ NiIII redox reaction at E 1/2 = +0.295 V (vs Ag/AgCl) in methanol solution. In a thin film with a free surface, complex (I) shows a fast photoelectric response upon exposure to visible light with a maximum photovoltage of ∼178 mV.

Vacancies in the molecular crystal of 2-(2'-hydroxyphenyl)benzothiazole

Structure of molecular units is calculated for the periodic model corresponding to the crystal lattice of 2-(2'-hydroxyphenyl)benzothiazole with vacancies. 2-(2' -hydroxyphenyl)benzothiazole is a luminescent organic substance undergoing excited state intramolecular proton transfer. The calculations are performed with density-functional based tight-binding methods usding Van der Waals interaction empirical correction. It is found that the dihedral angles formed by benzothiazole and phenol parts of the molecules deviate in the vicinity of the vacancy. The vacancy provides enough space for non-planar conformation of the molecules in the ground state. At the same time the increase in energy of the periodic structure with the vacancies caused by appearance of the non-planar conformation is larger than the corresponding increase in the isolated molecule.

Ethyl 4-oxo-1,4-dihydropyridine-3-carboxylate

The title compound, C8H9NO3, likely generated through hydrolysis and esterification of 3′-carboxy-3-methyl-(1,4′-bipyridin)-1-ium chloride by ethanol, which contained water, has a nearly planar conformation. The crystal structure is sustained by one-dimensional chains along the a-axis direction based on bifurcated N—H...(O,O) hydrogen bonds between the NH group of the 4-oxo-1,4-dihydropyridine ring and the two carbonyl O atoms.

Truxene Functionalized Star-Shaped Non-fullerene Acceptor With Selenium-Annulated Perylene Diimides for Efficient Organic Solar Cells

An electron acceptor with a truxene core and ring-fusion perylene diimide (PDI) tripolymer annulated by selenium (Se) branch, named as FTr-3PDI-Se, is designed and synthesized. FTr-3PDI-Se exhibits large conjugated planar conformation, strong absorption spectra in the regions of 300–400 and 450–550 nm, the deep HOMO energy level of 6.10 eV, and high decomposition temperature above 400°C. The FTr-3PDI-Se: PBDB-T-2Cl based device achieved a disappointing power conversion efficiency (PCE) of 1.6% together with a high Voc of 1.12 V. The low PCE was due to the large aggregates of blend film, the imbalanced hole/electron transport and low PL quenching efficiencies. The high Voc can be attributed to the high-lying LUMO level of FTr-3PDI-Se and the low-lying HOMO level of PBDB-T-2Cl. Our research presents an interesting and effective molecule-designing method to develop non-fullerene acceptor.

Crystal structure and fluorescence study of (μ-N-[(3,5-dimethyl-1H-pyrrol-2-yl)methylidene]-N-{4-[(3,5-dimethyl-1H-pyrrol-2-yl)methylideneazaniumyl]phenyl}azanium)bis[difluoridoboron(IV)]

The title molecule, C20H20B2F4N4, assumes a planar conformation with all atoms apart from the F atoms lying on the symmetry plane. Each boron atom is four-coordinated by two fluorine atoms, a pyrrole N atom and an imine N atom. Both imine CH=N groups adopt a trans conformation. In the crystal, the molecules self-assemble into a pillar structure through C—H...F hydrogen bonds and π–π interactions. The UV–vis spectrum and fluorescence spectra of the title compound are also reported.

Highly broadband NLO response of acceptor–donor–acceptor materials with a planar conformation

The third-order NLO properties of A–D–A molecules originally derived from organic photovoltaic (OPV) devices are studied. The results show that NLO performance of planar molecule (O-IDTBR) is better than that of twisted molecule (IDFBR) in solution or film state.

(3S,5R,6S)-Diphenylmethyl 1-oxo-6-bromopenicillanate

In the title compound, C21H20BrNO4S, a key intermediate in the synthesis of the widely used β-lactamase inhibitor tazobactam, the five-membered thiazolidine ring adopts an envelope conformation and the four-membered azetidine ring is in a distorted planar conformation. The crystal structure features C—H...O hydrogen bonds and a weak C—H...π interaction.

The amplified circularly polarized luminescence regulated from D–A type AIE-active chiral emitters via liquid crystals system

Two pairs of D–A type AIE-active chiral dyes doped into host 5CB form N*-LCs and regulate the amplified CPL signals. R-/S-2 with stronger D–A structure and more planar conformation could induce higher CPL response (glum = ±0.37) in N*-LCs system.

Luminescence properties and optimized structural conformations of the S0, S1 and T1 states of a tetranuclear formamidinate complex based on AuI and AgI metal ions

N,N′-Bis(pyridin-4-yl)formamidine (4-pyfH) was reacted with AuI and AgI metal salts to form a novel tetranuclear complex, tetrakis[μ-N,N′-bis(pyridin-4-yl)formamidinato]digold(I)disilver(I), [Ag2Au2(C11H9N4)2] or [Au x Ag4–x (4-pyf)4] (x = 0–4), 1, which is supported by its metallophilicity. Due to the potential permutation of the coordinated metal ions, six different canonical structures of 1 can be obtained. Complex 1 shows an emission at 501 nm upon excitation at 375 nm in the solid state and an emission at 438 nm upon excitation at 304 nm when dispersed in methanol. Time-dependent density functional theory (TD-DFT) calculations confirmed that these emissions can be ascribed to metal-to-ligand charge transfer (MLCT) processes. Moreover, the calculations of the optimized structural conformations of the S0 ground state, and the S1 and T1 excited states are discussed and suggest a distorted planar conformation for the tetranuclear Au2Ag2 complex.

Chemistry of Bridged Lactams: Recent Developments

Bridged lactams represent the most effective and wide-ranging method of constraining the amide bond in a non-planar conformation. A previous comprehensive review on this topic was published in 2013 (Chem. Rev. 2013, 113, 5701–5765). In the present review, which is published as a part of the Special Issue on Amide Bond Activation, we present an overview of the recent developments in the field of bridged lactams that have taken place in the last five years and present a critical assessment of the current status of bridged lactams in synthetic and physical organic chemistry. This review covers the period from 2014 until the end of 2018 and is intended as an update to Chem. Rev. 2013, 113, 5701–5765. In addition to bridged lactams, the review covers recent advances in the chemistry of bridged sultams, bridged enamines and related non-planar structures.