Additional Solvent Molecules Research Articles

Preparation of novel [Co(SCN)4] hybrid material: crystal structure investigation, DFT mechanistic analysis, antioxidant activity, and molecular docking study for potential inflammatory disorder control

The crystal structure of the title solvated coordination compound, [Co (SCN)4 (BtaH)2]·(BtaH)2.6(H2O), consists of discrete complexes in which the Co2+ cations are sixfold coordinated by four N-bonded thiocyanate anions and two 1-H benzotriazolium molecules to generate distorted trans-CoN6 octahedra. The discrete entities are each connected by three solvate molecules into chains via strong O—H···N hydrogen bonds. These chains are further linked by additional O—H···N, N—H···O, N—H···S, O—H···S and O—H···O hydrogen bonds into a three-dimensional network. Within this network, channels are formed that propagate along the c-axis direction and embed additional acetonitrile solvent molecules that are hydrogen-bonded to the network. In addition, density functional theory (DFT) calculations using the M06-2X/gen method were used to study the system's electronic properties. Interestingly, molecular docking and topological analyses were performed on compounds against various target anti-inflammatory receptors to investigate which targets exhibit the best binding affinities and hydrogen-bonding interactions. Done. As a result, it exhibits excellent anti-inflammatory activity, making it a suitable drug candidate for inflammatory diseases.

Novel dinuclear Ni (II) Schiff base complexes induced noncovalent exchanges: Crystal structure investigation, electrochemical assessment, Hirshfeld surface analysis and SARS‐CoV‐2 docking study

In this work, novel Ni (II) complexes, namely, [Ni2(L)2(OAc)2(EtOH)2] (1a), [Ni2(L)2(OAc)2(H2O)2] (1b‐1) and [Ni2(L)2(OAc)2(EtOH)2] (1b‐2) as co‐crystal were synthesized by the 1:1 condensation (https://www.sciencedirect.com/topics/chemistry/condensation) of Ni (CH3COO)2·4H2O and Schiff base ligand (H2L) (2‐hydroxy‐4‐methoxybenzaldehyde and 2‐amino‐2‐methylpropanol). The ligand based on Schiff base and fabricated complexes (1a) and (1b‐1 and 1b‐2) were successfully identified by CHN assessment, FT‐IR, UV–Vis spectra, melting point and CV voltammogram. The electrochemical behavior investigation shows that the nickel complexes exhibited irreversible oxidation processes in methanol solution. Additionally, the crystal structures of complexes (1a) and (1b) have been recognized by single‐crystal X‐ray diffraction investigation. It turned out that the complexes (1b‐1) and (1b‐2) crystallize together, making a co‐crystal 1b with an additional EtOH solvent molecule in the crystal structure. A detailed study of intermolecular exchanges was performed using attractive graphical analysis tools such as three‐dimensional Hirshfeld surfaces analysis, two‐dimensional fingerprint plots (FPs), and enrichment ratios (E), which make C‐H … C, C‐H … O hydrogen bond, C … O, H … H, and O … O short contacts on Hirshfeld surfaces with color code are observed. Moreover, an appraisement of the inhibitory trace against coronavirus (main protease SARS‐CoV‐2, PDB ID: 6Y2F) and molecular targets of human angiotensin‐converting enzyme‐2 (ACE‐2) was performed by a molecular docking study in which two nickel complexes performed best for PDB protein ID: 6M0J and all three complexes for PDB protein ID: 6Y2F.

Semirigid Ligands Enhance Different Coordination Behavior of Nd and Dy Relevant to Their Separation and Recovery in a Non-aqueous Environment.

Rare-earth elements are widely used in high-end technologies, the production of permanent magnets (PMs) being one of the sectors with the greatest current demand and likely greater future demand. The combination of Nd and Dy in NdFeB PMs enhances their magnetic properties but makes their recycling more challenging. Due to the similar chemical properties of Nd and Dy, their separation is expensive and currently limited to the small scale. It is therefore crucially important to devise efficient and selective methods that can recover and then reuse those critical metals. To address these issues, a series of heptadentate Trensal-based ligands were used for the complexation of Dy3+ and Nd3+ ions, with the goal of indicating the role of coordination and solubility equilibria in the selective precipitation of Ln3+–metal complexes from multimetal non-water solutions. Specifically, for a 1:1 Nd/Dy mixture, a selective and fast precipitation of the Dy complex occurred in acetone with the Trensalp-OMe ligand at room temperature, with a concomitant enrichment of Nd in the solution phase. In acetone, complexes of Nd and Dy with Trensalp-OMe were characterized by very similar formation constants of 7.0(2) and 7.3(2), respectively. From the structural analysis of an array of Dy and Nd complexes with TrensalR ligands, we showed that Dy invariably provided complexes with coordination number (cn) of 7, whereas the larger Nd experienced an expansion of the coordination sphere by recruiting additional solvent molecules and giving a cn of >7. The significant structural differences have been identified as the main premises upon which a suitable separation strategy can be devised with these kind of ligands, as well as other preorganized polydentate ligands that can exploit the small differences in Ln3+ coordination requirements.

Crystal structures, electrochemical properties and theoretical studies of three New Zn(II), Mn(III) and Co(III) Schiff base complexes derived from 2-hydroxy-1-allyliminomethyl-naphthalen

Three novel complexes of the Schiff base, 2-hydroxy-1-allyliminomethyl-naphthalen (HL), namely ZnII(HL)2 (1), polymeric [(MnIII(HL)2)(N3)2]n (2), and CoIII(HL)3 (3) were synthesized from the reaction of ZnBr2•2H2O, MnCl2•2H2O and Co(OAc)2•4H2O with the Schiff base ligand. The complexes were characterized by elemental analysis, FT-IR, UV-vis, as well as by the single-crystal X-ray diffraction technique. In all these complexes, central metal ions were coordinated by O and N atoms of the Schiff base ligand. It was found that the Zn complex (1) was C2-symmetrical, with the Zn ion in quite a regular tetrahedral environment. In turn, the Mn complex (2) made 1D-coordination polymer with N3 linkers between also symmetrical (Ci) Mn(HL)2 monomers, with six-coordinated Mn ion in an octahedral environment. Finally, the Co ion in Co(HL)3 complex (3) was also octahedrally 6-coordinated. Additional solvent (DMSO) molecules are built in the crystal architecture. The electrochemistry of complexes in DMSO displayed a metal-centered reduction peak corresponding to the ZnII/I- ZnI/0, MnIII/II- MnII/I, and CoIII/II - CoII/I at (-1.15,-1.53), (-0.11,-1.79) and (-0.76, -1.69) V, respectively. The molecular geometry of the complexes was optimized using the density functional theory with the basic set (B3LYP / 6-311G). After optimal DFT, the electron transfer spectrum was calculated theoretically and compared with the experimental results. Hirshfeld surfaces and fingerprint plots are used to visualize and analyze intermolecular interactions. The Hirshfeld surface analysis showed that the crystal cohesion of the structures of the three complexes is established via H•••H, C•••H/H•••C, and O•••H/H•••O the dominant contacts. As well as, molecular docking studies were carried out for all complexes to find their binding affinity with protein (PDB ID: 1LRI). Molecular binding studies have shown good interaction with the intended drug targets.

Synthesis and crystal structure of di-aqua-bis-(hexa-methyl-enetramine-κN)bis-(thio-cyanato-κN)cobalt(II)-hexa-methyl-ene-tetra-mine-aceto-nitrile (1/2/2).

The crystal structure of the title solvated coordination compound, [Co(NCS)2(C6H12N4)2(H2O)2]·2C6H12N4·2C2H3N, consists of discrete complexes in which the Co2+ cations (site symmetry ) are sixfold coordinated by two N-bonded thio-cyanate anions, two water mol-ecules and two hexa-methyl-ene-tetra-mine (HMT) mol-ecules to generate distorted trans-CoN4O2 octa-hedra. The discrete complexes are each connected by two HMT solvate mol-ecules into chains via strong O-H⋯N hydrogen bonds. These chains are further linked by additional O-H⋯N and C-H⋯N and C-H⋯S hydrogen bonds into a three-dimensional network. Within this network, channels are formed that propagate along the c-axis direction and in which additional aceto-nitrile solvent mol-ecules are embedded, which are hydrogen bonded to the network. The CN stretching vibration of the thio-cyanate ion occurs at 2062 cm-1, which is in agreement with the presence of N-bonded anionic ligands. XRPD investigations prove the formation of the title compound as the major phase accompanied by a small amount of a second unknown phase.

Effects of Ligand Substitution on the Optical and Electrochemical Properties of (Pyridinedipyrrolide)zirconium Photosensitizers.

A series of seven bis(pyridinedipyrrolide)zirconium complexes, Zr(R1PDPR2)2, where [R1PDPR2]2- is the doubly deprotonated form of [2,6-bis(5-R1-3-R2-1H-pyrrol-2-yl)pyridine], were prepared and characterized in solution by NMR, UV/vis absorption, and emission spectroscopy and cyclic voltammetry. The molecular structures were determined by single-crystal X-ray crystallography. All complexes exhibit remarkably long emission lifetimes (τ = 190-576 μs) with high quantum efficiencies (ΦPL = 0.10-0.38) upon excitation with visible light in a benzene solution. The substituents on the pyrrolide rings were shown to have significant effects on the photoluminescence and electrochemical properties of these compounds. The R2 substituents (R2 = H, Me, Ph, or C6F5) show only limited effects on the absorption and emission profiles of the complexes but allow systematic tuning of the ground- and excited-state redox potentials over a range of almost 600 mV. The R1 substituents (R1 = H, Me, Ph, or 2,4,6-Me3Ph) influence both the optical and electrochemical properties through electronic effects. Additionally, the R1 substituents have profound consequences for the structural flexibility and overall stability of the compounds. Distortions of the Zr(PDP)2 core from idealized D2d symmetry in the solid state can be traced to the steric profiles of the R1 substituents and correlate with the observed Stokes shifts for each compound. The complex with the smallest ligand system, Zr(HPDPH)2, coordinates two additional solvent molecules in a tetrahydrofuran (THF) solution, which allowed the isolation of photoluminescent, eight-coordinate Zr(HPDPH)2(THF)2. The photoredox catalytic dehalogenation of aryl iodides and aryl chlorides using the most reducing derivative, Zr(MePDPMe)2, highlights the potential of Zr(PDP)2 photosensitizers to promote challenging reductive transformations under mild conditions upon excitation with green light.

Synthesis, crystal structure and characterizations of di-μ-cyanido-1:2κ2 N:C;2:3κ2 C:N-bis-(4,7,13,16,21,24-hexa-oxa-1,10-di-aza-bicyclo-[8.8.8]hexacosa-ne)-1κ8 N 1,N 10,O 4,O 7,O 13,O 16,O 21,O 24;3κ8 N 1,N 10,O 4,O 7,O 13,O 16,O 21,O 24-[5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyrinato-2κ4 N]-2-iron(II)-1,3-dipotassium(I) tetra-hydro-furan disolvate with an unknown solvent.

The title compound, [Fe(C44H24N8Cl4)(CN)2][K2(C18H36N2O6)2]·2C4H8O was synthesized and characterized by single-crystal X-ray diffraction as well as FTIR and UV-vis spectroscopy. The central FeII ion is coordinated by four pyrrole N atoms of the porphyrin core and two C atoms of the cyano groups in a slightly distorted octa-hedral coordination environment. The complex mol-ecule crystallizes with two tetra-hydro-furan solvent mol-ecules, one of which was refined as disordered over two sets of sites with refined occupancies of 0.619 (5) and 0.381 (5). It has a distorted porphyrin core with mean absolute core-atom displacements Ca, Cb, Cm and Cav of 0.32 (3), 0.22 (3), 0.56 (2) and 0.37 (14) Å, respectively. The axial Fe-Ccyano bond lengths are 1.991 (2) and 1.988 (2) Å. The average Fe-Np (Np is a porphyrin N atom) bond length is 1.964 (10) Å. One of the O atoms and several C atoms of the 222 moiety [222 = 4,7,13,16,21,24-hexa-oxa-1,10-di-aza-bicyclo-[8.8.8]hexa-cosa-ne] were refined as disordered over two sets of sites with occupancy ratios of 0.739 (6):0.261 (6) and 0.832 (4):0.168 (4). Additional solvent mol-ecules were found to be highly disordered and their contribution to the scattering was removed using the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18], which indicated a solvent cavity of volume 372 Å3 containing approximately 83 electrons. These solvent mol-ecules are not considered in the given chemical formula and other crystal data.

Crystal structure of pyridinium tetra-iso-thio-cyanato-dipyridine-chromium(III) pyridine monosolvate.

In the crystal structure of the title compound, (C5H6N)[Cr(NCS)4(C5H5N)2]·C5H5N, the CrIII ions are octa-hedrally coordinated by four N-bonding thio-cyanate anions and two pyridine ligands into discrete negatively charged complexes, with the CrIII ion, as well as the two pyridine ligands, located on crystallographic mirror planes. The mean planes of the two pyridine ligands are rotated with respect to each other by 90°. Charge balance is achieved by one protonated pyridine mol-ecule that is hydrogen bonded to one additional pyridine solvent mol-ecule, with both located on crystallographic mirror planes and again rotated by exactly 90°. The pyridinium H atom was refined as disordered between both pyridine N atoms in a 70:30 ratio, leading to a linear N-H⋯N hydrogen bond. In the crystal, discrete complexes are linked by weak C-H⋯S hydrogen bonds into chains that are connected by additional C-H⋯S hydrogen bonding via the pyridinium cations and solvent mol-ecules into layers and finally into a three-dimensional network.

Unexpected reactions of NHC*-CuI and -AgI bromides with potassium thio- or seleno-cyanate.

The reactions of N-heterocyclic carbene CuI and AgI halides with potassium thio- or seleno-cyanate gave unexpected products. The attempted substitution reaction of bromido-(1,3-dibenzyl-4,5-di-phenyl-imidazol-2-yl-idene)silver (NHC*-Ag-Br) with KSCN yielded bis-[bis-(1,3-dibenzyl-4,5-di-phenyl-imidazol-2-yl-idene)silver(I)] tris-(thio-cyanato)-argentate(I) diethyl ether disolvate, [Ag(C29H24N2)2][Ag(NCS)3]·2C4H10O or [NHC*2Ag]2[Ag(SCN)3]·2Et2O, (1), while reaction with KSeCN led to bis-(μ-1,3-dibenzyl-4,5-diphenyl-2-seleno-imidazole-κ2 Se:Se)bis-[bromido-(1,3-dibenzyl-4,5-diphenyl-2-seleno-imid-azole-κSe)silver(I)] di-chloro-methane hexa-solvate, [Ag2Br2(C29H24N2Se)4]·6CH2Cl2 or (NHC*Se)4Ag2Br2·6CH2Cl2, (2), via oxidation of the NHC* fragment to 2-seleno-imidazole. This oxidation was observed again in the reaction of NHC*-Cu-Br with KSeCN, yielding catena-poly[[[(1,3-dibenzyl-4,5-diphenyl-2-seleno-imidazole-κSe)copper(I)]-μ-cyanido-κ2 C:N] aceto-nitrile monosolvate], {[Cu(CN)(C29H24N2Se)]·C2H3N} n or NHC*Se-CuCN·CH3CN, (3). Compound (1) represents an organic/inorganic salt with AgI in a linear coordination in each of the two cations and in a trigonal coordination in the anion, accompanied by diethyl ether solvent mol-ecules. The tri-blade boomerang-shaped complex anion [Ag(SCN)3]2- present in (1) is characterized by X-ray diffraction for the first time. Compound (2) comprises an isolated centrosymmetric mol-ecule with AgI in a distorted tetra-hedral BrSe3 coordination, together with di-chloro-methane solvent mol-ecules. Compound (3) exhibits a linear polymeric 1 ∞[Cu-C≡N-Cu-] chain structure with a seleno-imidazole moiety additionally coordinating to each CuI atom, and completed by aceto-nitrile solvent mol-ecules. Electron densities associated with an additional ether solvent mol-ecule in (1) and two additional di-chloro-methane solvent mol-ecules in (2) were removed with the SQUEEZE procedure [Spek (2015 ▸). Acta Cryst. C71, 9-18] in PLATON.

Crystal structure of [{FeCl3}2(μ-PCHP)2] [PCHP = 1,3-bis-(2-di-phenyl-phosphanyleth-yl)-3H-imidazol-1-ium] with an unknown solvent.

The crystal structure of the title compound, bis-{μ-1,3-bis-[2-(di-phenyl-phosphan-yl)eth-yl]-1H-imidazole-κ2 P:P'}bis-[tri-chlorido-iron(III)], [Fe2Cl6(C31H31N2P2)2] or [{FeCl3}2(μ-PCHP)2] (PCHP = C31H31N2P2), consists of dinuclear complexes that are located about centres of inversion. The FeIII cation is in a distorted trigonal-bipyramidal coordination with three chloride ligands located in the trigonal plane and two P atoms of symmetry-related PCHP ligands occupying the axial positions. Within the centrosymmetric complex, a pair of intra-molecular C-H⋯Cl hydrogen bonds between aromatic CH groups and chloride ligands are found. Individual complexes are linked into layers parallel to (01) by inter-molecular C-H⋯Cl hydrogen bonds. No pronounced inter-molecular inter-actions occur between these layers. This arrangement leaves space for disordered solvent mol-ecules. Electron density associated with these additional solvent mol-ecules was removed with the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18]. The given chemical formula and other crystal data do not take into account the unknown solvent mol-ecule(s).

Supramolecular Chemistry Based on Frustrated Lewis Pairs – Reactions of an Al/P FLP with Potassium Formate and Cesium Fluoride

Reactions of the Al/P‐based frustrated Lewis pair Mes2P–C(AltBu2)=C(H)–Ph (1) with the Brønstedt acids HBr, HI, and HCO2H resulted in the formation of the corresponding HXadducts Mes2(H)P–C[Al(X)tBu2]=C(H)–Ph [X= Br (4), I (5), OC(H)O (6)]. Despite the well‐known sensitivity of Al–C bonds towards protolysis, the products were isolated in good yields. Short intramolecular distances between H and Br, I or O are consistent with the presence of P–H···Xhydrogen bonds. Treatment of1with potassium formate or CsF yielded in poor to moderate yields the adducts Mes2P–C(AltBu2)=C(H)Ph·(KO2CH) (7) and Mes2P–C(AltBu2)=C(H)Ph·(CsF) (8). The potassium compounds required the presence of additional solvent molecules to obtain isolable crystalline products. Two monomeric units were joined by interactions of each K+cation with two formate anions. Supramolecular entities resulted by the additional coordination of the K+cations to solvent molecules (7a, toluene;7b, 1,2‐difluorobenzene;7c, THF), weak contacts to a mesityl group and in case of7band7cto atBu group and the P atom. The CsF adduct8crystallizes as a double‐stranded chain with the coordination of the Cs+cation to F–, a mesityl group (η6), a Ph group (η6; leads to an infinite chain), and atBu group (connects two chains to a double strand) of two different neighboring molecules. The Cs–F bond length is with 274.7(1) pm comparatively short, and the adduct may be viewed as a CsF molecule trapped by the FLP functionality.

Computational Elucidation of a Role That Brønsted Acidification of the Lewis Acid-Bound Water Might Play in the Hydrogenation of Carbonyl Compounds with H2 in Lewis Basic Solvents.

Brønsted acidification of water by Lewis acid (LA) complexation is one of the fundamental principles in chemistry. Using transition-state calculations (TS), herein we investigate the role that Brønsted acidification of the LA-bound water might play in the mechanism of the hydrogenation of carbonyl compounds in Lewis basic solvents under non-anhydrous conditions. The potential energy scans and TS calculations were carried out with a series of eight borane LAs as well as the commonly known strong LA AlCl3 in 1,4-dioxane or THF as Lewis basic solvents. Our molecular model consists of the dative LA-water adduct with hydrogen bonds to acetone and a solvent molecule plus one additional solvent molecule that participates is the TS structure describing the cleavage of H2 at acetone's carbonyl carbon atom. In all the molecular models applied here, acetone (O=CMe2 ) is the archetypical carbonyl substrate. We demonstrate that Brønsted acidification of the LA-bound water can indeed lower the barrier height of the solvent-involving H2 -cleavage at the acetone's carbonyl carbon atom. This is significant because at present it is believed that the mechanism of the herein considered reaction is described by the same mechanism regardless of whether the reaction conditions are strictly anhydrous or non-anhydrous. Our results offer an alternative to this belief that warrants consideration and further study.

Crystal structures of two 2,3-di-ethyl-naphtho-[2,3-g]quinoxaline-6,11-dione derivatives.

Two new 5,12-disubstituted 2,3-di-ethyl-naphtho-[2,3-g]quinoxaline-6,11-dione compounds were readily synthesized from the commercial dye quinizarin. For 2,3-diethyl-5,12-di-hydroxy-naphtho-[2,3-g]quinoxaline-6,11-dione, (II), C20H16N2O4, the mol-ecule displays a near planar conformation and both hy-droxy groups participate in intra-molecular O-H⋯O(carbon-yl) hydrogen bonds. In the crystal, π-π ring inter-actions [minimum ring centroid separation = 3.5493 (9) Å] form stacks of co-planar mol-ecules down the c axis, while only minor inter-molecular C-H⋯O inter-actions are present. In contrast, in 2,3-diethyl-5,12-bis-(piperidin-1-yl)naphtho-[2,3-g]quinoxaline-6,11-dione, (IV), C30H34N4O2, which contains two independent, but similar, mol-ecules in the asymmetric unit, the polycyclic cores have a significant twist, with dihedral angles of 29.79 (6) and 29.31 (7)° between the terminal rings and only minor inter-molecular C-H⋯O hydrogen-bonding inter-actions are present. Electron density associated with additional solvent mol-ecules disordered about a fourfold axis was accounted for using the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18].

Crystal Inclusion Formation of a New Type of Dumbbell-Shaped Host Compound Featuring Two Bulky 2,3,4,5-Tetraphenylcyclopenta-2,4-dien-1-ol Terminal Groups Attached to a Linear Spacer Unit

Four new host compounds of dumbbell shape featuring bulky 2,3,4,5-tetraphenylcyclopenta-2,4-dien-1-ol moieties attached to both ends of a linear spacer element of different lengths comprising both 1,4-phenylene and ethynylene subunits are synthesized and corresponding crystal inclusions involving DMSO, DMF, MeCN, and THF as guest solvents (seven examples of inclusion compounds) are isolated. X-ray structural analysis shows the formation of 1:2 host/guest entities being a basic supramolecular motif of the crystal inclusions. Nevertheless, additional solvent molecules seem to be necessary for stabilization of the crystal structure in most cases of the inclusion species indicating the occurrence of unusually high stoichiometric ratios of included solvent as a specific characteristic of the new type of host molecule.

Beyond Time-Dependent Density Functional Theory Using Only Single Excitations: Methods for Computational Studies of Excited States in Complex Systems.

Single-excitation methods, namely, configuration interaction singles and time-dependent density functional theory (TDDFT), along with semiempirical versions thereof, represent the most computationally affordable electronic structure methods for describing electronically excited states, scaling as [Formula: see text] absent further approximations. This relatively low cost, combined with a treatment of electron correlation, has made TDDFT the most widely used excited-state quantum chemistry method over the past 20+ years. Nevertheless, certain inherent problems (beyond just the accuracy of this or that exchange-correlation functional) limit the utility of traditional TDDFT. For one, it affords potential energy surfaces whose topology is incorrect in the vicinity of any conical intersection (CI) that involves the ground state. Since CIs are the conduits for transitions between electronic states, the TDDFT description of photochemistry (internal conversion and intersystem crossing) is therefore suspect. Second, the [Formula: see text] cost can become prohibitive in large systems, especially those that involve multiple electronically coupled chromophores, for example, the antennae structures of light-harvesting complexes or the conjugated polymers used in organic photovoltaics. In such cases, the smallest realistic mimics might already be quite large from the standpoint of ab initio quantum chemistry. This Account describes several new computational methods that address these problems. Topology around a CI can be rigorously corrected using a "spin-flip" version of TDDFT, which involves an α → β spin-flipping transition in addition to occupied → virtual excitation of one electron. Within this formalism, singlet states are generated via excitation from a high-spin triplet reference state, doublets from a quartet, etc. This provides a more balanced treatment of electron correlation between ground and excited states. Spin contamination is problematic away from the Franck-Condon region, but we describe a "spin-complete" version of the theory in which proper spin eigenstates are obtained by construction. For systems of coupled chromophores, we have developed an ab initio version of the Frenkel-Davydov exciton model in which collective excitations of the system are expanded in a basis of excited states computed for individual chromophores. The monomer calculations are trivially parallelizable, as is computation of the coupling matrix elements needed to construct the exciton Hamiltonian, and systems containing hundreds of chromophores can be tackled on commodity hardware. This enables calculations on organic semiconductors, where even small model systems exhibit a semicontinuum of excited states that renders traditional TDDFT computationally challenging. Despite including only single excitations on each monomer, the exciton model can describe entangled spins on two or more monomers, an effect that is responsible for excitation energy transfer between chromophores, for example, in singlet fission. Excitonic approximations can also be applied to the TDDFT equations themselves, and a particularly promising application is to describe the effects of environment on an excitation that is localized on a single chromophore. This "local excitation approximation" to TDDFT allows an essentially arbitrary number of solvent molecules to be included in the calculation in a highly parallelizable way such that the time-to-solution increases only very slowly as additional solvent molecules are added. It is therefore possible to converge the calculation with respect to describing an ever-larger portion of the environment at a quantum-mechanical level.

Crystal structure of ethyl 3-amino-6-methyl-2-[(4-methyl-phen-yl)carbamo-yl]-4-[(E)-2-phenyl-ethen-yl]thieno[2,3-b]pyridine-5-carboxyl-ate monohydrate.

In the title mol-ecule, C27H25N3O3S·H2O, the dihedral angle between the planes of the thienyl ring and the pendant p-tolyl group is 39.25 (6)°, while that between the pyridine ring and the pendant phenyl ring is 44.37 (6)°. In addition, there is a slight twist in the bicyclic core, with a dihedral angle of 2.39 (4)° between the thienyl and pyridine rings. The conformation of the carbamoyl moiety is partially determined by an intra-molecular N-H⋯O hydrogen bond. In the crystal, complementary N-H⋯O hydrogen bonds form dimers which are then associated into chains parallel to the c axis through O-H⋯N hydrogen bonds involving the water mol-ecule of crystallization. Electron density associated with an additional solvent mol-ecule of partial occupancy and disordered about a twofold axis was removed with the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18]. The given chemical formula and other crystal data do not take into account the unknown solvent molecule(s).

The different conformations and crystal structures of dihydroergocristine

The identification of different forms of dihydroergocristine (DHEC) was carried out by crystallization from different organic solvents. DHEC was identified as potential template for molecularly imprinted polymers (MIPs) for the epimeric specific analysis of ergot alkaloids (EAs) in food. DHEC was crystallized from different solvents in order to mimic the typical MIP synthesis conditions. Four new solvatomorphs of DHEC were obtained. All solvatomorphs contain a water molecule in the crystal structure, whereas three compounds contain an additional solvent molecule. Based on the conformation of DHEC a comparison with typical EA molecules was possible. The analysis showed that DHEC is a suitable template for MIPs for EAs.

Tetranuclear Cu(II) and Ni(II) complexes with 1,3,5-triketone ligands: A quantum-chemical simulation of exchange interactions

A series of tetranuclear copper and nickel coordination compounds based on 1,3,5-triketone ligands is calculated using the B3LYP/6-31G(d,p) method of the density functional theory. The antiferromagnetic exchange is predicted to be in all studied complexes, regardless of the type of the metal, the size of linker groups, and the presence of additional solvent (pyridine) molecules. The Ni(II) complexes are characterized by weak exchange interactions, which makes it possible to consider them as candidates for the development of spin qubits.

Polymerization accompanied by the formation of colloidal particles and gels: 1. Kinetics of spatially inhomogeneous radical polymerization

The kinetic model of radical polymerization is based on the assumptions that highly exothermic chain propagation (addition of the monomer to the growing macroradical) is a diffusion-controlled reaction and chain transfer (addition of solvent molecule S to the macroradical to form oligomers and regenerate the primary radical) is an activated kinetic reaction involving S from the nearest environment of the macroradical. The chain propagation rate is determined by the flow of the monomer from the reaction volume into the capture sphere, on the surface of which macroradicals of any length have a quasi-steady-state concentration. The capture sphere is a source of oligomers diffusing from it into the reaction volume. It has been shown that a decrease in the diffusion coefficients with increasing oligomer chain length and increasing local viscosity (due to accumulation of oligomers) leads to a spatially inhomogeneous molecular-mass distribution: long oligomers concentrate in the vicinity of the macroradical and the short ones are built up in the remote zone. The polymerization ends by the formation of “primary blobs” in which the concentration of the monomer (in the oligomer composition) is several orders of magnitude above that in the initial solution.

Hydrogen bonding of the naphthalene radical cation to water and methanol and attachment of the naphthalene ion to extended hydrogen bonding chains

The binding energies of water and methanol to the naphthalene radical cation (7.8 and 8.3kcal/mol, respectively) are reported. The naphthalene ion forms unconventional carbon-based ionic hydrogen bonds with H2O and CH3OH (CHδ+⋯OH2 and CHδ+⋯OHCH3, respectively) which can be extended to hydrogen bonding chains with additional solvent molecules. Both water and methanol molecules show a strong tendency for the external solvation of the naphthalene cation. These structures allow the PAH ion to reside on the surface of ice grains in interstellar medium where reactions with incoming organic molecules could take place to produce a variety of complex organics in space.