Five years after we published the synthesis of the first diamidocarbene (DAC)-supported amino borylene 4, we now report the elusive single crystal X-ray structure. The X-ray structure of 4 was found to corroborate our previous computational studies which indicated that the borylene adopted a heterocumulenic geometry with a near linear C(carbene) = B = N unit (175.88(18)◦) as well as short C = B and B = N distances of 1.416(3) and 1.344(3) Å, respectively. Additionally, we further provide a qualitative and quantitative discourse on said structure with respect to the precursor compounds used to prepare 4 as well as to the known cyclic (alkyl) amino carbene (CAAC) analog 2.

Hybrid moieties of ethynylated-thiourea, Th1 and Th2 have been synthesised via the addition reaction between ethynyl derivatives and 4-tert-butylbenzoyl isothiocyanate in acetone, and were characterised by selected spectroscopic methods (i.e., 1H and 13C NMR, UV–visible, FT-IR) and elemental analysis. Thermogravimetric analysis indicated that Th1 and Th2 were relatively stable up to ca. 210 °C. Single-crystal X-ray diffraction was used to identify the crystal structure of Th2 in which the centre of 1-acyl thiourea moiety (-C(O)NHC(S)NH) exhibits S conformation. The Hirshfeld surface analysis has allowed visualizing the crystal packing, which is characterised by the prolonged intermolecular N–H⋯O = C and N–H⋯S = C hydrogen-bonding interactions within Th2 molecule. Electrochemical data of both compounds correspondingly exhibit irreversible redox potential processes. Besides, frontier molecular orbitals and Natural Bond Orbital population analysis were computed at the B3LYP/6-31G (d, p) level of approximation, suggesting strong delocalization of the electronic density through a conjugated π-system involving the ethynyl-phenyl and thiourea groups.Graphical AbstractFigure of molecular structure for acyl thiourea-ethynyl derivative. Two derivatives of acyl thiourea-ethynyl were synthesised and characterised by selected spectroscopic methods such as 1H and 13C NMR, UV-visible, FT-IR, elemental, thermal, electrochemical, X-ray diffraction, and density functional theory (DFT) calculation for molecular orbitals and natural bond orbital population analysis.

AbstractThe crystal structure of a novel bis(ligand)copper(II) complex of the pyridine-2-carboxaldehyde 2-furoyl hydrazone (HPCFur) metallophore is described, altogether with its Hirshfeld surface analysis. The isolated compound crystallizes in the monoclinic system, space group P21/c, with four [Cu(PCFur)2] molecules in the asymmetric unit. Symmetry around copper is distorted octahedral. HPCFur coordinates in its deprotonated, iminolate form, which impacts the O1−C7 and N2−N3 distances in both ligand units. The complex exhibits a variety of weak, non-conventional intermolecular hydrogen bonds. Hirshfeld analysis and fingerprint plots indicate that, overall, hydrogen bond interactions are responsible for almost 50% of the crystal 3D arrangement, while nondirectional H···H contacts account for 38.0%. To the best of our knowledge, this is the first description of a copper(II) complex containing this ligand. The structural characterization of this poorly water soluble species contributes to a better understanding of the intricate equilibria that take place in biologically relevant ternary peptide/protein-copper-hydrazone systems.Graphical Abstract

The novel third-order nonlinear optical organic material 4-fluoro-N-[4-(diethylamino)benzylidene]aniline (FDEABA) is synthesized and single crystals of FDEABA are grown using the slow evaporation method. The placement of the protons is confirmed by nuclear magnetic resonance spectral analysis. Employing Fourier transform infrared spectral analysis, vibrational frequencies of various functional groups of the FDEABA compound are identified. The three-dimensional crystal structure of the grown crystal is elucidated using single crystal X-ray diffraction studies, which reveal that the compound FDEABA crystallized in the monoclinic non-centrosymmetric space group P21. Intermolecular interactions are studied using Hirshfeld surface analysis and compared with similar structures of halogen-substituted benzylideneaniline derivatives. Thermal stability of FDEABA is measured using thermogravimetric and differential thermal analyses and the melting point of the synthesized FDEABA compound is 51 °C. Open aperture Z-scan measurements carried out at 532 nm using 5 ns laser pulses reveal nonlinear optical absorption leading to strong optical limiting behaviour, which can be useful in the protection of eyes and sensitive optical detectors from harmful laser radiation.Graphical Abstract

A novel Co(II) complex [Co4(HL)2Phen2(H2O)10]·20(H2O) (HL = 5-(Bis-carboxymethyl-amino)-isophthalic acid; Phen = 1,10-Phenanthroline) was synthesized by hydrothermal methods, and its crystal structure was determined by single-crystal X-ray diffraction. The title complex crystallized in the monoclinic space group C2/c as an isolated tetranuclear structure. The strong π···π stacking, hydrogen bonding and van de Waals attractions produce 3D supramolecular structure. A series of properties of the title complex were tested by solid-state photoluminescence, CIE analysis and solid-state diffuse reflectance. The results show that the title complex is blue light emitter, CIE (0.2172, 0.5581) and has an energy bandwidth of 2.33 eV.Graphical AbstractA novel monoclinic space group C2/c complex of [Co4(L)2Phen2(H2O)10]·20(H2O) (HL = 5-(Bis-carboxymethyl-amino)-isophthalic acid; Phen = 1,10-Phenanthroline) was synthesized by hydrothermal methods, and a series of properties of the complex were tested by solid-state photoluminescence, CIE analysis and solid-state diffuse reflectance, which results show that the title complex is blue light emitter, CIE (0.2172, 0.5581) and has an energy bandwidth of 2.33 eV.

Three new cyanide-bridged heterobimetallic complexes {[Cu(L)]2[Cr(CN)5(NO)]}ClO4·2H2O (1), {{[Cu(cyclam)][Fe(CN)5(NO)]}·H2O}n (2), {{[Cu(cyclam)]3[Cr(CN)5(NO)]2}·CH3OH·4H2O}n (3) (L=2,12-dimethyl-3,7,11,17-tetraazabicyclo [11.3.1] heptadeca-1 (17), 13, 15-triene, cyclam=1,4,8,11-tetraazacyclodecane) have been successfully assembled from the pentacyanometalates and two copper(II) compounds and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. X-ray structural analysis revealed that the Complex 1 is a cationic trinuclear CrCu2 entity with the positive charge balanced by ClO4− ion, while complexes 2 and 3 were structurally characterized showing a 1D chain. The magnetic properties of the reported cyanide-bridged complexes have been experimentally studied and theoretically simulated, disclosing the ferromagnetic interaction between the Cr(I) ion and the Cu(II) ion through the cyanide bridge.Graphical Abstract

Two new hybrid solids viz. {Hpz}2[H7CrMo6O24]·6H2O (1) and [Co(2-Hampz)2Cl4] (2) have been crystallized via solvent evaporation technique using pyrazole (pz) and 2-aminopyrazine (2-ampz) respectively. The solids were characterized using single crystal X-ray diffraction, fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy and thermal analysis. The solid 1 crystallized in orthorhombic system with space group Pbca, a = 23.1796(8), b = 11.1281(4), c = 25.1499(9) Å, Z = 8. The solid 2 crystallized in triclinic system with space group P-1, a = 7.1986(5), b = 7.3917(5), c = 7.8896(6) Å, α = 115.758(3), β = 110.450(3), γ = 96.904(3)°, Z = 1. While, solid 1 is a new Anderson–Evans cluster based solid, 2 is a new pseudopolymorph of cobalt complex [Co(2-ampz)4Cl2]. Crystal structure analysis suggested that supramolecular interactions facilitate the crystal packing in solids 1 and 2. In addition, the role of synthetic parameters in dictating the nature of self-assembly of solids 1 and 2 in aqueous medium has also been analyzed.Graphical AbstractAn Anderson–Evans cluster based solid, {Hpz}2[H7CrMo6O24]·6H2O (1) and a new pseudopolymorph of cobalt complex [Co(2-ampz)4Cl2] viz. [Co(2-Hampz)2Cl4] (2) have been synthesized using pyrazole (pz) and 2-aminopyrazine (2-ampz) respectively.

Utilizing the facile addition–elimination reaction of thiosemicarbazide with acetone or aldehydes, nine thiosemicarbazones were synthesized. Aldehydes were chosen which contain additional heteroatoms to increase the diversity of possible intermolecular interactions. Further, the thiosemicarbazone synthesis was conducted in situ with one of the common halogen bond donors 1,2-, 1,3-, or 1,4-diiodotetrafluorobenzene, 1,3,5-trifluoro-2,4,6-triiodobenzene, or tetraiodoethylene. These reactions resulted in the characterization of 12 new cocrystals showcasing halogen bonding. The dimerization of two thiosemicarbazone units through a pair of N‒H···S hydrogen bonds was a universal feature of the solid-state structures in this series, with the hydrogen bond network often extending these motifs into chains. The organoiodines serve to link chains through either I···S or I···N halogen bonding, or less commonly, S···I chalcogen bonding. This variety of intermolecular interactions leads to the formation of double-stranded chains, ribbons, and sheets.Graphical AbstractUtilizing the facile addition–elimination reaction of thiosemicarbazide with acetone or aldehydes, nine thiosemicarbazones were synthesized, seven of which were isolated as cocrystals with common halogen bond donors. Significant N–H···S hydrogen bonding was observed in all, with S···I halogen and chalcogen bonding contributing to the long-range packing in the cocrystals.

The reaction between bis(phosphino)ferrocene, [Fe{C5H4P(C6H4CH2NMe2-o)2}2] (1) and AgOTf resulted in disilver complex [(AgOTf)2{µ-Fe{C5H4P(C6H4CH2NMe2)2}2}] (2) which on further treatment with 2,2′-bipyrdine yielded a mixed-ligand complex [Ag2(bipy)2{µ-Fe{C5H4P(C6H4CH2NMe2)2}2}](OTf)2 (3). Reaction of 1 with AuCl(SMe2) in 1:2 molar ratio afforded a digold complex [(AuCl)2Fe{C5H4P(C6H4CH2NMe2)2}2] (4). Treatment of 4 with anhydrous CdCl2 resulted in heterometallic complex [Fe{C5H4P(AuCl)(C6H4CH2NMe2)2(CdCl2)}2] (5). The reactions of 1 with anhydrous CdI2 and HgI2 in 1:2 molar ratios yielded bimetallic complexes [Fe{C5H4P(CdI2)(C6H4CH2NMe2)2}2] (6) and [Fe{C5H4P(HgI2)(C6H4CH2NMe2)2}2] (7), respectively. The molecular structures of 3, 4 and 7 were confirmed by single crystal X-ray analysis. Complexes 3 and 7 crystallized in the triclinic space group with P-1, whereas 4 crystallized in the monoclinic space group with C2/c. Single crystals suitable for X-ray crystallography were obtained using diffusion method where a solution of [Fe{C5H4P(C6H4CH2NMe2)2}2] (1) in dichloromethane was layered on a solution of CdI2 and HgI2 in methanol and stored at room temperature for 24 h, resulted in yellow plates of 6 and 7, respectively. All complexes crystallized with the asymmetric unit containing half a molecule and with the Fe atom on an inversion centre. A Hirshfeld surface analysis indicated that the most significant contributions to the crystal packing of 3 are from H‧‧‧H (50.2%), C‧‧‧H/H‧‧‧C (8.3%), Cl‧‧‧H/H‧‧‧Cl (12.1%), O‧‧‧H/H‧‧‧O (11.3%), F‧‧‧H/H‧‧‧F (9.0%) contacts, while those for 4 are from H‧‧‧H (73.7%), C‧‧‧H/H‧‧‧C (8.9%), Cl‧‧‧H/H‧‧‧Cl (14.5%), Au‧‧‧H/H‧‧‧Au (1.8%) and N‧‧‧H/H‧‧‧N (0.8%) contacts, and those for 7 are from H‧‧‧H (65.5%), C‧‧‧H/H‧‧‧C (6.6%), I‧‧‧H/H‧‧‧I (24.1%) and I‧‧‧C/C‧‧‧I (2.9%) contacts.Graphical Abstract Crystal structures of silver(I), gold(I) and mercury(II) complexes containing [Fe{C5H4P(C6H4CH2NMe2)2}2] (1) are described.

Abnormal carbene complex of Pd(L1)2, where L1 = 1,3-Bis(2,6-diisopropylphenyl)-2,4-diphenylimidazole and normal carbene complex of Pd(L2)2, where L2 = 1,3-dimesityl-4,9-dioxonaphtho-2,3-diimidazole were prepared from a Pd(0) precursor Pd(COD)(CH2TMS)2. Both the complexes crystalize in the triclinic space group P-1 and cell parameters of Pd(L1)2 and Pd(L2)2 are a = 12.0477 Å, b = 17.5269 Å, c = 18.9786 Å, α = 114.4855°, β = 92.5295°, γ = 107.9472° and a = 11.5007 Å, b = 15.2316 Å, c = 17.9007 Å, α = 67.061°, β = 72.143°, γ = 72.183° respectively. In both case N-heterocyclic ligands are distorted towards palladium direction. Further, crystal structures reveal that the palladium atom is covalently bonded to the two aNHC and nNHC ligands respectively. The electrochemical properties of these complexes were determined by cyclic voltammetry analysis in THF solution under argon atmosphere. The enunciated reversibility of the complexes can be explained by sequential one electron oxidations of the palladium centre from Pd(0) to Pd(I) and then Pd(II).Graphical AbstractAbnormal carbene complex of Pd(L1)2, where L1 = 1,3-Bis(2,6-diisopropylphenyl)-2,4-diphenylimidazole and normal carbene complex of Pd(L2)2, where L2 = 1,3-dimesityl-4,9-dioxonaphtho-2,3-diimidazole were prepared from a Pd(0) precursor of Pd(COD)(CH2TMS)2. The crystal structures were determined by single crystal X-ray diffraction data and electrochemical properties were also determined by cyclic voltammetric analysis.

Reactions of two dialkyl-substituted pyrazine ligands with a triosmium cluster are described. Both 2-ethyl-3-methylpyrazine (C4H2N2MeEt) and 2,5-dimethylpyrazine (C4H2N2Me2) react with the labile triosmium cluster [Os3(CO)10(NCMe)2] at 80 °C to afford [HOs3(CO)10(µ-C4HN2MeEt)] (1) and [HOs3(CO)10(µ-C4HN2Me2)] (2), respectively. Clusters 1 and 2 are formed via C–H bond activation at the α-carbon of the corresponding pyrazine ligand. Cluster 2 reacts with PPh3 at room temperature in the presence of Me3NO‧2H2O to yield the mono- and diphosphine-substituted clusters [HOs3(CO)9(PPh3)(µ-C4HN2Me2)] (3) and [HOs3(CO)8(PPh3)2(µ-C4HN2Me2)] (4), respectively, both of which exist in more than one isomeric form in solution. All new clusters have been characterized using spectroscopic methods together with single-crystal X-ray diffraction studies for 1, 2, and 4. The bonding in these clusters have been investigated by electronic structure calculations.Graphical AbstractTwo new triosmium clusters bearing a metalated pyrazine ligand have been synthesized and structurally characterized. The reactivity of one of these newly synthesized clusters towards PPh3 has also been investigated.

The crystal structure of the thiosemicarbazide derivative 4-cyclohexyl-1-(thiophene-2-carbonyl)thiosemicarbazide (ChtcTSC), C12H17N3OS2, is reported here. The title compound ChtcTSC has been characterized by various physicochemical techniques viz UV–Vis., Infrared, and NMR. It crystallizes in the monoclinic system having space group P21/c. The dihedral angle between the thiophene and cyclohexyl rings is 60.7(4)°. The crystal packing is established by intermolecular N–H⋯O packing interactions involving a three-center donor hydrogen bond between the keto oxygen atom of the thiophene group and H atoms belonging to the hydrazine group which links the molecules into chains along the (011) plane of the unit cell. Hydrogen bonds between the hydrazine hydrogen atom and one of the thiophene groups and C–H⋯Cg π -ring interactions provide added stability to the crystal packing. The fingerprint plots associated with Hirshfeld surface analysis indicate that there are different types of weak interactions viz. O⋯H–C, O⋯H–N, and S⋯H–C. The geometry optimization has been performed using the DFT method, and geometrical parameters thus obtained for ChtcTSC correlate with the single-crystal X-ray data. The TD-DFT study showed a small HOMO and LUMO energy gap of 2.869 eV. The electronic transition from the ground state to the excited state due to a transfer of electrons from HOMO to LUMO levels is mainly associated with the n → π* transition.Graphical AbstractThe crystal structure of 4-cyclohexyl-1-(thiophene-2-carbonyl)thiosemicarbazide (ChtcTSC) is reported here where the title compound ChtcTSC has been characterized by various physiochemical techniques including UV–Vis., Infrared, NMR, DFT and Hirshfeld surface analysis.

Recrystallization of [Zn(malt)2(H2O)1.5] (malt = maltolato(-1), C6H5O3) from a concentrated aqueous solution acidified with HCl to pH 3.0 yielded colorless crystals of [Zn(Hmalt)2Cl2] (Hmalt = neutral maltol, C6H6O3). The Zn(II) site exhibits distorted tetrahedral coordination through bonding to two chloride ligands and to two neutral maltol ligands, each bonding through the ketonic oxygen. [Zn(Hmalt)2Cl2] is a unique example of a neutral monodentate coordination by the maltol ligand.Graphical AbstractA view of the tetrahedral [Zn(Hmalt)2Cl2] (Hmalt = neutral maltol, C6H6O3).

The crystal structures of di-μ-chlorobis[2-(5-methyl-pyridin-2-yl-κN)phenyl-κC(1)] diplatinum(II) (1) and chloro(N,N-dimethylformamide-κO)[2-(5-methyl-pyridin-2-yl-κN)phenyl-κC(1)]platinum(II) (2) have been determined by means of the X-ray diffraction. Both complexes cocrystallize in the monoclinic space group C2/c with a = 39.5457(18) Å, b = 7.2482(4) Å, c = 21.2269(10) Å and β = 121.460(2)°. The asymmetric unit consists of half a centrosymmetric compound (complex 1) and one full independent compound (complex 2).Graphical AbstractThe X-ray structures of co-crystallized di-μ-chlorobis[2-(5-methyl-pyridin-2-yl-κN)phenyl-κC(1)]diplatinum(II) (1) as starting material and of the derivative chloro(N,N-dimethylformamide-κO)[2-(5-methyl-pyridin-2-yl-κN)phenyl-κC(1)]platinum(II) (2) are reported.

The preparation and characterization of two supramolecular complexes from octahedral [Ta6Cl12(CN)6]4−/3− units and 2, 2′: 6′, 2″-terpyridine (Terpy) metal complexes as building blocks are reported. Single crystal analyses revealed [Mn(Terpy)]2[Ta6Cl12(CN)6]·MeOH (1) features a neutral two-dimensional (2D) framework composed of layers based on [Ta6Cl12(CN)6]4− and [Mn(Terpy)]2+. Each layer is built of 6-connected [Ta6Cl12]2+ and 3-connected Mn(II) nodes bridged by cyanide ligands. The layers are held together by MeOH molecules. The layered structure is maintained after the removal of solvent molecule (MeOH) upon heating, leading to the formation of [Mn(Terpy]2[Ta6Cl12(CN)6] (1′). In the case of using Gd3+, the resultant product was revealed by single-crystal analyses to be an ionic compound [Gd(Terpy)(H2O)4(DMF)2][Ta6Cl12(CN)6]⋅DMF ⋅3H2O (2). 2 has a three-dimensional (3D) framework built of [Gd(Terpy)(H2O)4(DMF)2]3+ and [Ta6Cl12(CN)6]3− ions connected to each other via extensive hydrogen bonds and π-π interactions between the cations, anions, and solvent molecules. Thermal stabilities of 1‒2 are reported.Graphical AbstractThe X-ray structures and thermal stabilities of a coordination polymer [Mn(Terpy)]2[Ta6Cl12(CN)6] ⋅MeOH and an ionic compound [Gd(Terpy)(H2O)4(DMF)2][Ta6Cl12(CN)6]⋅DMF⋅3H2O are presented.

Ferrocenylbis(phosphonites), [Fe(C5H4P(OR)2)2 (2, R = -C6H4(OMe-o); 3, R = -C6H4(C3H5-o))] were synthesized by the reaction of Fe(C5H4PCl2)2 (1) with 2-methoxyphenol and 2-allylphenol. The reaction of 2 with elemental selenium afforded bisselenide, [Fe{C5H4P(Se)(OC6H4(OMe-o))2}2] (4). Equimolar reaction between 3 and [RuCl2(η6-p-cymene)]2 yielded [{Ru2Cl4(η6-p-cymene)2}Fe{C5H4P(OC6H4(C3H5-o))2}2] (5) in good yield. Bisselenide (4) and ruthenium(II) complex (5) were characterized by single-crystal X-ray analysis. In compound 4, the geometry around phosphorus atoms is distorted tetrahedral. In case of complex 5, ruthenium atoms containing η6-p-cymene, two chlorides and one phosphine moiety display a typical three-legged "piano-stool" structure. The molecule has crystallographically imposed centrosymmetry. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing of compound 4 are from H⋅⋅⋅H (50.1%), C⋅⋅⋅H/H⋅⋅⋅C (24.1%), Se⋅⋅⋅H/H⋅⋅⋅Se (13.4%), O⋅⋅⋅H/H⋅⋅⋅O (10.8%) contacts, and in the case of complex 5 are from H⋅⋅⋅H (73.3%), C⋅⋅⋅H/H⋅⋅⋅C (15.8%), Cl⋅⋅⋅H/H⋅⋅⋅Cl (10%) contacts.Graphical AbstractThis paper describes crystal structures of bisselenide and a ruthenium(II) complex [Fe{C5H4P(Se)(OC6H4(OMe-o))2}2 and [{RuCl2(η6-p-cymene)}2Fe{C5H4P(OC6H4(C3H5-o))2}2].

The new compound 4-hydroxy-1-[(4-nitrophenyl)sulfonyl]pyrrolidine-2-carboxyllic acid was obtained by the reaction of 4-hydroxyproline with 4-nitrobenzenesulfonyl chloride. The compound was characterized using single crystal X-ray diffraction studies. Spectroscopic methods including NMR, FTIR, ES-MS, and UV were employed for further structural analysis of the synthesized compound. The title compound was found to have crystallized in an orthorhombic crystal system with space group P212121. The S1-N1 bond length of 1.628 (2) Å was a strong indication of the formation of the title compound. The absence of characteristic downfield 1H NMR peak of pyrrolidine ring and the presence of S–N stretching vibration at 857.82 cm−1 on the FTIR are strong indications for the formation of the sulfonamide. The experimental study was complemented with computations at the B3LYP/6-311G + + (d,p) level of theory to gain more understanding of interactions in the compound at the molecular level. Noncovalent interaction, Hirsfeld surface analysis and interaction energy calculations were employed in the analysis of the supramolecular architecture of the compound. Predicted ADMET parameters, awarded suitable bioavailability credentials, while the molecular docking study indicated that the compound enchants promising inhibition prospects against dihydropteroate synthase, DNA topoisomerase, and SARS-CoV-2 spike. Graphical AbstractHerein we present the solid state structure, noncovalent interaction and spectroscopic analysis of a prospective bioactive compound 4-hydroxy-1-[(4-nitrophenyl)sulphonyl]pyrrolidine-2-carboxyllic acid.

AbstractTwo new hybrid iodobismuthates, [C8H17N2][C10H22N2][BiI6] (1) and [C6H12N2]0.5[C10H22N2]3.5[Bi2I10][Bi2I9] (2), have been prepared by solvothermal synthesis in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) and ethanol. Both compounds have been characterized by single-crystal and powder X-ray diffraction, infrared and UV–Vis spectroscopies and thermogravimetric analysis. Structure determination reveals that the crystal structure of 1 contains mononuclear [BiI6]3− anions, whilst 2 contains an unusual combination of dinuclear anions, [Bi2I9]3− and [Bi2I10]4−, consisting of two edge- and two face-sharing [BiI6]3− octahedra, respectively. Mono- and diethylated derivatives of DABCO, which are formed in situ under solvothermal conditions, act as countercations and are located between the discrete anions. The optical band gaps of 1 and 2, which are 2.29(1) and 2.03(2) eV respectively, are consistent with the red color of these compounds, and are comparable to the band gaps measured for other iodobismuthates containing discrete anions.Graphical AbstractTwo new iodobismuthates, [C8H17N2][C10H22N2][BiI6] (1) and [C6H12N2]0.5[C10H22N2]3.5[Bi2I10][Bi2I9] (2), have been synthesized under solvothermal conditions, and their crystal structures determined by single-crystal X-ray diffraction.

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.Graphical AbstractEthoxy–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.Graphical AbstractCrystal 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+.