Intermolecular interaction characteristics of the Boron-nitrogen rings,and with hexagonal boron nitride: A special molecular adsorption and weak interaction

With the discovery of cyclo[18]carbon, related theoretical research has become a very hot topic. Due to its unique molecular structure, many derivatives have been derived, especially its isoelectronic molecule cyclo B₉N₉. This work focused on the interaction between cyclo B₉N₉ molecules and explored the nature of their interaction. The interaction of the dimer of cyclo B₉N₉ was studied, quantum chemical calculation and wave function analysis were carried out, and compared with cyclo[18]carbon to find its commonness. It showed that the interaction between the cyclo B₉N₉ dimers is a weak electron generating stacking interaction. In addition, the adsorption of cyclo B₉N₉ was studied, and the interaction of graphene analogues hexagonal boron nitride (h-BN). Through calculation and analysis, it was found that the adsorption of cyclo B₉N₉ was much stronger than that of cyclo[18]carbon. In another sense, the π–π stacking interaction of boron nitrogen structure is stronger than that of carbon. To further validate this commonality, B₆N₆ was selected for the same calculation, and similar conclusions were obtained. It was also found that the more Boron nitrogen (BN), the stronger the stacking interaction.     

3‐(tert‐Butyl­oxy­carbonyl­amino)­bicyclo­[1.1.1]­pentane­carboxyl­ic acid at 293 K

In the room‐temperature X‐ray structure of the N‐Boc‐protected derivative of the novel 3‐amino­bi­cyclo[1.1.1]­pentanecarboxyl­ic acid, C₁₁H₁₇NO₄, the interbridgehead distance in the bi­cyclo­[1.1.1]­pentane cage is 1.852 (2) Å. The carboxyl and parts of the blocked amino group are almost in plane with one of the cage triangles. N—H?O and O—H?O hydrogen bonds generate infinite corrugated molecular chains in the crystal lattice.     

Crystal structure and DFT calculations of Cp2NbH(SiIMe2)(SiFMe2): an asymmetric bis(silyl) niobocene hydride complex

An asymmetric bis(silyl) niobocene hydride complex, namely, bis(η⁵-cyclopentadienyl)(fluorodimethylsilyl)hydrido(iododimethylsilyl)niobium, [Nb(C₅H₅)₂(C₂H₆FSi)(C₂H₆ISi)H] or Cp₂NbH(SiIMe₂)(SiFMe₂), has been studied to determine the effect of the silyl ligand on the position of the hydride attached to the Nb atom. It has been shown that when a Group 17 atom is substituted onto one of the silyl ligands, there is a greater interaction between the hydride and this ligand, as demonstrated by a shorter Si…H distance. In the present work, we have investigated the effect when the silyl ligands are substituted by different Group 17 atoms. We present here the structure and DFT calculations of Cp₂NbH(SiIMe₂)(SiFMe₂), showing that the position of the hydride is located between the two silyl ligands. The results from our investigation show that the hydride is closer to the silyl ligand that is substituted by fluorine.     

Theoretical study of isomerism of compounds of N2 and N2H2 molecules with aluminum clusters Al13 and Al12Ti

Segments of the potential energy surfaces corresponding to successive elementary stages of multistep fragmentation of nitrogen and diimine molecules upon their reaction with the aluminum cluster Al₁₃ and its doped analogue Al₁₂Ti have been calculated by the density functional theory method. The minimum energy pathways of these reactions have been calculated for the stages of physisorption, chemisorption, and N₂ and N₂H₂ fragmentation with different ways of insertion of fragments into the Al₁₃ and Al₁₂Ti cages. Relative energies, structural characteristics, and vibrational frequencies of coordinated and fragment isomers have been calculated, the barriers separating these isomers have been evaluated, and molecular diagrams of the reactions have been constructed. The effect of doping on the relative energies of intermediates and activation barriers has been considered. A conclusion has been drawn that doping with titanium should facilitate the reactions of molecular nitrogen with aluminum clusters. Unusual isomers with a five- and six-coordinate nitrogen atom N* have been localized. The results are compared with the data of analogous previous calculations of the PES of isomers corresponding to stepwise fragmentation of an acetylene molecule in related Al₁₃C₂H₂ and Al₁₂TiC₂H₂ derivatives.     

The Influence of Chemical Composition of Fullerenes on the Structural Features and Conformational Preference of Encapsulated Disilane Molecule

The study of the structure and conformational properties of the disilane molecule in the C₈₀ and B₄₇N₃₃ fullerene cavities using the PBE/3ζ DFT method showed that the encapsulated molecule contains a shortened Si–Si bond, carries a certain electric charge, and exhibits a noticeable increase in the potential barrier to rotation around the Si–Si bond. At the same time, in the case of fullerene Si₆₀, the observed effects, with the exception of the electric charge on the guest molecule, do not appear. For the Si₂H₆@C₆₀ system, in the course of geometry optimization, a virtual reaction of disilane with the carbon skeleton of the nanoobject occurs with Si–Si bond cleavage and the formation of two SiH₃ fragments bonded to fullerene carbon atoms.     

The structures of 1,4‐diaryl‐5‐trifluoromethyl‐1H‐1,2,3‐triazoles related to J147, a drug for treating Alzheimer's disease

J147 [N‐(2,4‐dimethylphenyl)‐2,2,2‐trifluoro‐N′‐(3‐methoxybenzylidene)acetohydrazide] has recently been reported as a promising new drug for the treatment of Alzheimer's disease. The X‐ray structures of seven new 1,4‐diaryl‐5‐trifluoromethyl‐1H‐1,2,3‐triazoles, namely 1‐(3,4‐dimethylphenyl)‐4‐phenyl‐5‐trifluoromethyl‐1H‐1,2,3‐triazole (C₁₇H₁₄F₃N₃, 1 ), 1‐(3,4‐dimethylphenyl)‐4‐(3‐methoxyphenyl)‐5‐trifluoromethyl‐1H‐1,2,3‐triazole (C₁₈H₁₆F₃N₃O, 2 ), 1‐(3,4‐dimethylphenyl)‐4‐(4‐methoxyphenyl)‐5‐trifluoromethyl‐1H‐1,2,3‐triazole (C₁₈H₁₆F₃N₃O, 3 ), 1‐(2,4‐dimethylphenyl)‐4‐(4‐methoxyphenyl)‐5‐trifluoromethyl‐1H‐1,2,3‐triazole (C₁₈H₁₆F₃N₃O, 4 ), 1‐[2,4‐bis(trifluoromethyl)phenyl]‐4‐(3‐methoxyphenyl)‐5‐trifluoromethyl‐1H‐1,2,3‐triazole (C₁₈H₁₀F₉N₃O, 5 ), 1‐(3,4‐dimethoxyphenyl)‐4‐(3,4‐dimethoxyphenyl)‐5‐trifluoromethyl‐1H‐1,2,3‐triazole (C₁₉H₁₈F₃N₃O₄, 6 ) and 3‐[4‐(3,4‐dimethoxyphenyl)‐5‐(trifluoromethyl)‐1H‐1,2,3‐triazol‐1‐yl]phenol (C₁₇H₁₄F₃N₃O₃, 7 ), have been determined and compared to that of J147 . B3LYP/6‐311++G(d,p) calculations have been performed to determine the potential surface and molecular electrostatic potential (MEP) of J147 , and to examine the correlation between hydrazone J147 and the 1,2,3‐triazoles, both bearing a CF₃ substituent. Using MEPs, it was found that the minimum‐energy conformation of 4 , which is nearly identical to its X‐ray structure, is closely related to one of the J147 seven minima.     

Four‐ and five‐coordinate copper(II) complexes with N‐(4,4‐diphenyl‐5‐oxo‐4,5‐dihydro‐1H‐imidazol‐2‐yl)glycine

The two title mononuclear compounds are four‐coordinate bis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C₁₇H₁₄N₃O₃)₂]·2C₃H₇NO, (I), and five‐coordinate aquabis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C₁₇H₁₄N₃O₃)₂(H₂O)]·2C₃H₇NO, (II). In (I), the Cu^II ion lies on an inversion centre with one‐half of the complex molecule in the asymmetric unit, while in (II) there are two independent ligand molecules in the asymmetric unit, with the Cu^II ion and coordinated water molecule located on a general position. In both crystal structures, the complex molecules assemble in ribbons via N—H...O hydrogen‐bond networks.     

Four 2‐amino‐6‐aryl‐4‐methoxy‐11H‐pyrimido[4,5‐b][1,4]benzodiazepines: similar molecular structures but different crystal structures

2‐Amino‐4‐methoxy‐6‐phenyl‐11H‐pyrimido[4,5‐b][1,4]benzodiazepine, C₁₈H₁₅N₅O, (I), and its 6‐(2‐fluorophenyl)‐, 6‐(3‐nitrophenyl)‐ and 6‐(4‐methoxyphenyl)‐ analogues, viz. C₁₈H₁₄FN₅O, (II), C₁₈H₁₄N₆O₃, (III), and C₁₉H₁₇N₅O₂, (IV), respectively, all adopt molecular conformations which are almost identical, containing boat‐shaped seven‐membered rings. In each structure, paired N—H...N hydrogen bonds link the molecules into centrosymmetric dimers. In each of (I)–(III), the dimers are further linked, forming a different three‐dimensional framework in each case, while in compound (IV) the dimers are linked into sheets. The significance of this study lies in the observation of different crystal structures in four compounds whose molecular structures are very similar.     

Counter‐anion role in the formation of two supramolecular complexes: [Ag2(DPP)2](ClO4)2·CH3CN and [Ag2(DPP)2(NO3)2] {DPP is N‐[(diphenylphosphanyl)methyl]pyridin‐4‐amine}

The title compounds, bis{μ‐N‐[(diphenylphosphanyl)methyl]pyridin‐4‐amine‐κ²N¹:P}disilver bis(perchlorate) acetonitrile monosolvate, [Ag₂(C₁₈H₁₇N₂P)₂](ClO₄)₂·CH₃CN, (1), and bis{μ‐N‐[(diphenylphosphanyl)methyl]pyridin‐4‐amine‐κ²N¹:P}bis[(nitrato‐κ²O,O)silver], [Ag₂(C₁₈H₁₇N₂P)₂(NO₃)₂], (2), each contain disilver macrocyclic [Ag₂(C₁₈H₁₇N₂P)₂]²⁺ cations lying about inversion centres. The cations are constructed by two N‐[(diphenylphosphanyl)methyl]pyridin‐4‐amine (DPP) ligands linking two Ag⁺ cations in a head‐to‐tail fashion. In (1), the unique Ag⁺ cation has a near‐linear coordination geometry consisting of one pyridine N atom and one P atom from two different DPP ligands. Two ClO₄⁻ anions doubly bridge two metallomacrocycles through Ag...O and N—H...O weak interactions to form a chain extending in the c direction. The half‐occupancy acetonitrile molecule lies with its methyl C atom on a twofold axis and makes a weak N...Ag contact. In (2), there are two independent [Ag(C₁₈H₁₇N₂P)]⁺ cations. The nitrate anions weakly chelate to each Ag⁺ cation, leading to each Ag⁺ cation having a distorted tetrahedral coordination geometry consisting of one pyridine N atom and one P atom from two different DPP ligands, and two chelating nitrate O atoms. Each dinuclear [Ag₂(C₁₈H₁₇N₂P)₂(NO₃)₂] molecule acts as a four‐node to bridge four adjacent equivalent molecules through N—H...O interactions, forming a two‐dimensional sheet parallel to the bc plane. Each sheet contains dinuclear molecules involving just Ag1 or Ag2 and these two types of sheet are stacked in an alternating fashion. The sheets containing Ag1 all lie near x = , , etc, while those containing Ag2 all lie near x = 0, 1, 2 etc. Thus, the two independent sheets are arranged in an alternating sequence at x = 0, , 1, etc. These two different supramolecular structures result from the different geometric conformations of the templating anions which direct the self‐assembly of the cations and anions.     

Three new olanzapine structures: the acetic acid monosolvate,and the propan‐2‐ol and propan‐2‐one hemisolvate monohydrates

The crystal structures of three new solvates of olanzapine [systematic name: 2‐methyl‐4‐(4‐methylpiperazin‐1‐yl)‐10H‐thieno[2,3‐b][1,5]benzodiazepine], namely olanzapine acetic acid monosolvate, C₁₇H₂₀N₄S·C₂H₄O₂, (I), olanzapine propan‐2‐ol hemisolvate monohydrate, C₁₇H₂₀N₄S·0.5C₃H₈O·H₂O, (II), and olanzapine propan‐2‐one hemisolvate monohydrate, C₁₇H₂₀N₄S·0.5C₃H₆O·H₂O, (III), are presented and compared with other known olanzapine forms. There is a fairly close resemblance of the molecular conformation for all studied analogues. The crystal structures are built up through olanzapine dimers, which are characterized via C—H...π interactions between the aliphatic fragment (1‐methylpiperazin‐4‐yl) and the aromatic fragment (benzene system). All solvent (guest) molecules participate in hydrogen‐bonding networks. The crystal packing is sustained via intermolecular N_host—H...O_guest, O_guest—H...N_host, O_guest—H...O_guest and C_host—H...O_guest hydrogen bonds. It should be noted that the solvent propan‐2‐ol in (II) and propan‐2‐one in (III) show orientational disorder. The propan‐2‐ol molecule lies close to a twofold axis, while the propan‐2‐one molecule resides strictly on a twofold axis through the carbonyl C atom. In both cases, the water molecules present positional disorder of the H atoms.     

A combinatorial chemistry approach to new materials for non‐linear optics. I. Five Schiff bases

A combinatorial chemistry approach has been used to synthesize an array of Schiff bases, five of which, namely N‐[(E,2E)‐3‐(4‐methoxy­phenyl)‐2‐propenyl­idene]‐3‐nitro­aniline, C₁₆H₁₄N₂O₃, (1a), N‐[(E,2E)‐3‐(4‐methoxy­phenyl)‐2‐propenyl­idene]‐4‐nitro­aniline, C₁₆H₁₄N₂O₃, (2a), N‐{(E,2E)‐3‐[4‐(di­methyl­amino)­phenyl]‐2‐propenyl­idene}‐3‐nitro­aniline, C₁₇H₁₇N₃O₂, (1b), N‐{(E,2E)‐3‐[4‐(di­methyl­amino)­phenyl]‐2‐propenyl­idene}‐4‐nitro­aniline, C₁₇H₁₇N₃O₂, (2b), and N‐{(E,2E)‐3‐[4‐(di­methyl­amino)­phenyl]‐2‐propenyl­idene}‐2‐methyl‐4‐nitro­aniline, C₁₈H₁₉N₃O₂, (3b), have been structurally characterized. A stack structure is observed for (1a) and (1b) in the crystal phase. Experimental and calculated molecular structures are discussed for these compounds which belong to a chemical class having potential applications as non‐linear optical materials.     

Formation of aniline-like ions by electron-impact-induced elimination of CO from formanilide

The metastable peak intensity ratios for elimination of HNC vs DNC from the [M ? CO]⁺· ion of deuterium labelled analogues of formanilide show that the formyl hydrogen atom migrates to nitrogen prior to or during CO expulsion to form a [C₆H₇N]⁺· ion of aniline-like structure. An examination of metastable peaks does not allow similar conclusions to be reached for methyl substituted formanilides. Low abundance [C₆H₆O]_+· ions are formed by HNC elimination from the formanilide molecular ion in a reaction where three covalent bonds to the formyl carbon are broken.     

Studies in organometallic rearrangements IV—proton and carbon nuclear magnetic resonance spectra of group IVA substituted indenes and indenyl anions

The proton and carbon NMR spectra for a series of substituted indenes [C₉H₇R, R = H, CH₃, Si(CH₃)₃] are reported. The proton and carbon resonances for the 5-membered ring exhibit pronounced changes as a function of the substituents.     

Two (E)‐2‐({[4‐(dialkylamino)phenyl]imino}methyl)‐4‐nitrophenols

The slow evaporation of analytical NMR samples resulted in the formation of crystals of (E)‐2‐({[4‐(dimethylamino)phenyl]imino}methyl)‐4‐nitrophenol, C₁₅H₁₅N₃O₃, (I), and (E)‐2‐({[4‐(diethylamino)phenyl]imino}methyl)‐4‐nitrophenol, C₁₇H₁₉N₃O₃, (II). Despite the small structural difference between these two N‐salicylideneaniline derivatives, they show different space groups and diverse molecular packing. The molecules of both compounds are close to being planar due to an intramolecular O—H...N hydrogen bond. The 4‐alkylamino‐substituted benzene ring is inclined at an angle of 13.44 (19)° in (I) and 2.57 (8)° in (II) with respect to the 4‐nitro‐substituted phenol ring. Only very weak intermolecular π–π stacking and C—H...O interactions were found in these structures.     

Geometry and bond‐length alternation in nonlinear optical materials. II. Effects of donor strength in two push–pull molecules

The compounds N‐[2‐(4‐cyano‐5‐dicyanomethylene‐2,2‐dimethyl‐2,5‐dihydrofuran‐3‐yl)vinyl]‐N‐phenylacetamide, C₂₀H₁₆N₄O₂,(I), and 2‐{3‐cyano‐5,5‐dimethyl‐4‐[2‐(piperidin‐1‐yl)vinyl]‐2,5‐dihydrofuran‐2‐ylidene}malononitrile 0.376‐hydrate, C₁₇H₁₈N₄O·0.376H₂O, (II), are novel push–pull molecules. The significant bonding changes in the polyene chain compared with the parent molecule 2‐dicyanomethylene‐4,5,5‐trimethyl‐2,5‐dihyrofuran‐3‐carbonitrile are consistent with the relative electron‐donating properties of the acetanilido and piperidine groups. The packing of (I) utilizes one phenyl–cyano C—H...N and two phenyl–carbonyl C—H...O hydrogen bonds. Compound (II) crystallizes with a partial water molecule (0.376H₂O), consistent with cell packing that is dominated by attractive C—H...N(cyano) interactions. These compounds are precursors to novel nonlinear optical chromophores, studied to assess the impact of donor strength and the extent of conjugation on bond‐length alternation, crystal packing and aggregation.     

Binuclear dinitrogen complexe of aryl- and benzyldicyclopentadienyltitanium(III) compounds

The preparation of the deep-blue diamagnetic dinitrogen complexes (Cp₂TiR)₂N₂ with R=C₆H₅, o-, m-, p-CH₃C₆H₄, C₆F₅, CH₂C₆H₅ is described. Their chemical and physcial properties confirm the formulation in which the R groups are σ-bonded to the Cp₂Ti moiety, and the two nitrogen atoms are equivalent. The heats of formation of the complexes from Cp₂TiR and N₂ in toluene have been determined from spectrophotometric data; for R=C₆H₅, o-, m-, p-CH₃C₆H₄, C₆F₅, CH₂C₆H₅, the values are ?18, ?9, ?17, ?20, ?17 and ?14 kcal·mol^?1, respectively. The solid complexes vary markedly in thermal stability, and are extremely air sensitive. The complexed nitrogen can be completely reduced with sodium naphthalene; after hydrolysis of the products, NH₃ and N₂H₄ are obtained. In the thermolysis of the solids, some of the nitrogen is reduced.     

A concise synthesis of a highly substituted 6‐(1H‐benzimidazol‐1‐yl)‐5‐nitrosopyrimidin‐2‐amine: synthetic sequence and the molecular and supramolecular structures of one product and two intermediates

A concise and efficient synthesis of 6‐benzimidazolyl‐5‐nitrosopyrimidines has been developed using Schiff base‐type intermediates derived from N⁴‐(2‐aminophenyl)‐6‐methoxy‐5‐nitrosopyrimidine‐2,4‐diamine. 6‐Methoxy‐N⁴‐{2‐[(4‐methylbenzylidene)amino]phenyl}‐5‐nitrosopyrimidine‐2,4‐diamine, (I), and N⁴‐{2‐[(ethoxymethylidene)amino]phenyl}‐6‐methoxy‐5‐nitrosopyrimidine‐2,4‐diamine, (III), both crystallize from dimethyl sulfoxide solution as the 1:1 solvates C₁₉H₁₈N₆O₂·C₂H₆OS, (Ia), and C₁₄H₁₆N₆O₃·C₂H₆OS, (IIIa), respectively. The interatomic distances in these intermediates indicate significant electronic polarization within the substituted pyrimidine system. In each of (Ia) and (IIIa), intermolecular N—H…O hydrogen bonds generate centrosymmetric four‐molecule aggregates. Oxidative ring closure of intermediate (I), effected using ammonium hexanitratocerate(IV), produced 4‐methoxy‐6‐[2‐(4‐methylphenyl‐1H‐benzimidazol‐1‐yl]‐5‐nitrosopyrimidin‐2‐amine, C₁₉H₁₆N₆O₂, (II) [Cobo et al. (2018). Private communication (CCDC 1830889). CCDC, Cambridge, England], where the extent of electronic polarization is much less than in (Ia) and (IIIa). A combination of N—H…N and C—H…O hydrogen bonds links the molecules of (II) into complex sheets.     

Synthesis and characterization of (cryptand‐222)potassium (2‐methylimidazolato)(meso‐tetraphenylporphinato)ferrate(II)–2‐methylimidazole–tetrahydrofuran (1/1/2)

Metalloporphyrin complexes containing an additional imidazole ligand can provide information about the effect of deprotonation or hydrogen bonding on the axial histidine unit in heme proteins. The title high‐spin five‐coordinate imidazolate‐ligated iron(II) porphyrinate, [K(C₁₈H₃₆N₂O₆)][Fe(C₄H₅N₂)(C₄₄H₂₈N₄)]·C₄H₆N₂·2C₄H₈O, has been synthesized and investigated. The solvated salt crystallizes with one 2‐methylimidazole molecule, two tetrahydrofuran solvent molecules and a potassium cation chelated inside a cryptand‐222 (4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane) molecule. The imidazolate ligand is ordered. The average Fe—Np (Np is a porphyrin N atom) bond length is 2.113 (11) Å and the axial Fe—N_Im (N_Im is an imidazolate N atom) is 2.0739 (13) Å. The out‐of‐plane displacement of the Fe^II atom from the 24‐atom mean plane is 0.6098 (5) Å, indicating an apparent doming of the porphyrin core.     

Almotriptan,an antimigraine agent,and its malate salt

The crystal structures of almotriptan {systematic name: N,N‐dimethyl‐2‐[5‐(pyrrolidin‐1‐ylsulfonylmethyl)‐1H‐indol‐3‐yl]ethanamine}, C₁₇H₂₅N₃O₂S, and almotriptan malate {systematic name: N,N‐dimethyl‐2‐[5‐(pyrrolidin‐1‐ylsulfonylmethyl)‐1H‐indol‐3‐yl]ethanaminium malate, C₁₇H₂₆N₃O₂S⁺·C₄H₅O₅⁻, a novel selective serotonin 1B/D agonist, have been determined in order to gain further insight into the structure–activity relationships of triptans. The two structures differ in the orientation of their sulfonylpyrrolidine side chains. A comparison with other triptans reveals that molecules of almotriptan, sumatriptan, zolmitriptan and rizatriptan can adopt two principal conformations. N—H...N, N—H...O and O—H...O hydrogen bonds are responsible for the molecular packing.     

Four cytotoxic N4‐substituted thiosemicarbazones derived from 2‐hydroxynaphthalene‐1‐carboxaldehyde

The X‐ray crystal structures are reported of four novel and potentially O,N,S‐tridentate donor ligands that demonstrate antitumour activity. These ligands are 1‐[(4‐methyl­thio­semicarbazono)methyl]‐2‐naphthol, C₁₃H₁₃N₃OS, (III), 1‐[(4‐ethylthio­semicarbazono)­methyl]‐2‐naphthol, C₁₄H₁₅N₃OS, (IV), 1‐[(4‐phenyl­thio­semicarbazono)­methyl]‐2‐naphthol, C₁₈H₁₅N₃OS, (V), and 1‐[(4,4‐di­methyl­thio­semicarbazono)­methyl]‐2‐naphthol di­methyl sulfoxide solvate, C₁₄H₁₅N₃OS·C₂H₆OS, (VI). These chelators are N4‐substituted thio­semicarbazones, each based on the same parent aldehyde, namely 2‐­zhydroxynaphthalene‐1‐carboxaldehyde isonicotinoylhydrazone. Conformational variations within this series are discussed in relation to the optimum conformation for metal‐ion binding.