Supramolecular assembly based on “emerging” intermolecular interactions of particular interest to coordination chemists

Redetermination of the crystal structure of bis(μ2-di-ethyldithiocarbamato-κ3 S,S′:S;κ3 S:S: S′)-hexacarbonyl-di-rhenium(I), C16H20N2O6Re2S4

C16H20N2O6Re2S4, monoclinic, C2/c (no. 15), a = 15.3490(2) Å, b = 11.79920(10) Å, c = 13.33770(10) Å, β = 103.9980(10)°, V = 2343.80(4) Å3, Z = 4, R gt(F) = 0.0166, wR ref(F 2) = 0.0445, T = 100(2) K.

Crystal structure of dibromidobis(4-bromobenzyl)tin(IV), C14H12Br4Sn

C14H12Br4Sn, monoclinic, I2/a (no. 15), a = 12.6379(2) Å, b = 4.9674(1) Å, c = 26.1845(4) Å, β = 94.507(1)°, V = 1638.71(5) Å3, Z = 4, R gt(F) = 0.0142, wR ref(F 2) = 0.0358, T = 100 K.

Solvent-driven structural topology involving energetically significant intra- and intermolecular chelate ring contacts and anticancer activities of Cu(ii) phenanthroline complexes involving benzoates: experimental and theoretical studies

Two new coordination solids [Cu2(μ2-Bz)4(CH3OH)2][Cu2(η2-Bz)2(phen)2(H2O)2]·(NO3)2 (1) and [Cu(phen)(H2O)(Bz)(η2-Bz)] (2) (phen = 1,10-phenanthroline; Bz = benzoate) have been synthesized and characterized using elemental analysis, TGA, spectroscopic (IR, UV-vis-NIR and ESR) and single crystal X-ray diffraction techniques. Change of the solvent from methanol to DMF results in changes in the architectures that are triggered by a change from square pyramidal to octahedral coordination at the divalent metal centers for complexes 1 and 2 respectively. The structural topology of the complexes is established by the interplay of strong O-H⋯O and weak C-H⋯O, C-H⋯C, π-π stacking interactions. Unconventional parallel intramolecular and anti-parallel intermolecular contacts involving the chelate rings (CR) also stabilize the structures. The energetic analyses of the structures evidence that the parallel arrangement is energetically favoured which is likely due to the presence of the Cu⋯Cu cuprophilic interaction in 1 that is not established in 2. Compound 1 exhibits the highest antibacterial activity against Rhizobium leguminosarum among the tested cultures. In vitro cytotoxicity and apoptosis studies were carried out for compounds 1 and 2 on malignant Dalton's lymphoma cell line (DL). Both compounds showed a significant effect on the decrease in cell viability as compared to a control, while compound 2 induced remarkable cytotoxicity towards DL cells. Treatment also showed the appearance of membrane blebbing, chromatin condensation and fragmented nuclei which are typical characteristic features of apoptotic cell death. Furthermore, a docking study revealed that both compounds docked in the active sites of all the cancer target proteins under study. Moreover, SAR analysis revealed that oxygen and nitrogen atoms of compound 1 and the oxygen atoms of compound 2 are crucial for biological activities.

A Ternary Nickel(II) Schiff Base Complex Containing Di-anionic and Neutral Forms of a Dithiocarbazate Schiff Base

The title NiII complex, Ni(L)(LH2) (1), where LH2 is S-2-methybenzyl-β-N-(2-hydroxy-3-methoxybenzylmethylene) dithiocarbazate, was isolated from the reaction of Ni(acetate)2·4H2O and two molar equivalents of LH2. The complex was characterized by elemental analysis, spectroscopy (IR and UV) as well as by a single-crystal X-ray structure determination. The nickel(II) center is coordinated within a cis-NOS2 donor set that defines a square planar geometry. Three donor atoms, i.e., N, O, and S, are provided by a doubly deprotonated S-2-methybenzyl-β-N-(2-hydroxy-3-methoxybenzylmethylene) dithiocarbazate ligand while the fourth donor, i.e., a thione-S, comes from the neutral form of the dithiocarbazate ligand. In the LH2 ligand, an intramolecular hydroxy-O-H…N(imine) hydrogen bond is found. There is also an intra-ligand, charge assisted amine-N-H…O(phenoxide) hydrogen bond. A notable feature of the molecular packing is the formation of supramolecular chains sustained by π…π stacking interactions whereby the interacting rings are the five- and six-membered chelate and methoxybenzene rings. The chains are connected into a three-dimensional architecture by methyl-C-H…O(methoxy), methoxy-C-H…S(ester), and tolyl-C-H…π(tolyl) interactions.

Intramolecular Metal⋅⋅⋅π-Arene Interactions in Neutral and Cationic Main Group Compounds

The role of intramolecular metal⋅⋅⋅π-arene interactions has been investigated in the solid-state structures of a series of main group compounds supported by the bulky amide ligands, [N(^tBu Ar^≠ )(SiR₃ )]^- (^tBu Ar^≠ =2,6-(CHPh₂ )₂ -4-tBuC₆ H₂ , R=Me, Ph). The lithium and potassium amide salts showed different patterns of solvation and demonstrated that the SiPh₃ substituent is able to be involved in stabilizing the electrophilic metal. These group 1 metal compounds served as ligand transfer reagents to access a series of bismuth(III) halides. Chloride extraction from Bi(N{^tBu Ar^≠ }{SiPh₃ })Cl₂ using AlCl₃ afforded the 1:1 salt [Bi(N{^tBu Ar^≠ }{SiPh₃ })Cl][AlCl₄ ]. This was accompanied by a significant rearrangement of the stabilizing π-arene contacts in the solid-state. Attempted preparation of the corresponding tetraphenylborate salt resulted in phenyl-transfer and generation of the neutral Bi(N{^tBu Ar^≠ }{SiPh₃ })(Ph)Cl.

Blue-emitting bolaamphiphilic zwitterionic iridium(iii) complex

Aggregation induced emission is a very interesting phenomenon that recently has attracted a lot of interest. Most of the examples deal with organic molecules or flat metal complexes. Here we demonstrate that, by design, even iridium compounds can display this process without shifting the emission energy. In order to enhance the aggregation properties we have focussed on amphiphilic complexes. We report the synthesis and photophysical characterisation of a blue-emitting bolaamphiphilic zwitterionic Ir(iii) complex and an analogous cationic amphiphilic compound, used as a reference. The bolaamphiphile exhibited blue (λmax = 450 nm) emission in dilute, deaerated solution with a photoluminescence quantum yield (PLQY) of 22%, similar to the related cationic amphiphilic complex. The bolaamphiphile displayed significant emission enhancement in the solid state, with an emission quantum yield that reach 52%. Interestingly, the emission of the cationic analogue suffers from aggregation quenching in the solid state, (PLQY = 3%) as is common for these type of complexes. A correlation between the photophysical data and the arrangement in the solid state is discussed.

Utilizing Hirshfeld surface calculations, non-covalent inter-action (NCI) plots and the calculation of inter-action energies in the analysis of mol-ecular packing

The analysis of atom-to-atom and/or residue-to-residue contacts remains a favoured mode of analysing the mol-ecular packing in crystals. In this contribution, additional tools are highlighted as methods for analysis in order to complement the 'crystallographer's tool', PLATON [Spek (2009). Acta Cryst. D65, 148-155]. Thus, a brief outline of the procedures and what can be learned by using Crystal Explorer [Spackman & Jayatilaka (2009). CrystEngComm 11, 19-23] is presented. Attention is then directed towards evaluating the nature, i.e. attractive/weakly attractive/repulsive, of specific contacts employing NCIPLOT [Johnson et al. (2010). J. Am. Chem. Soc. 132, 6498-6506]. This is complemented by a discussion of the calculation of energy frameworks utilizing the latest version of Crystal Explorer. All the mentioned programs are free of charge and straightforward to use. More importantly, they complement each other to give a more complete picture of how mol-ecules assemble in mol-ecular crystals.

o-Vanillin Derived Schiff Bases and Their Organotin(IV) Compounds: Synthesis, Structural Characterisation, In-Silico Studies and Cytotoxicity

Six new organotin(IV) compounds of Schiff bases derived from S-R-dithiocarbazate [R = benzyl (B), 2- or 4-methylbenzyl (2M and 4M, respectively)] condensed with 2-hydroxy-3-methoxybenzaldehyde (oVa) were synthesised and characterised by elemental analysis, various spectroscopic techniques including infrared, UV-vis, multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR and mass spectrometry, and single crystal X-ray diffraction. The organotin(IV) compounds were synthesised from the reaction of Ph₂SnCl₂ or Me₂SnCl₂ with the Schiff bases (S2MoVaH/S4MoVaH/SBoVaH) to form a total of six new organotin(IV) compounds that had a general formula of [R₂Sn(L)] (where L = Schiff base; R = Ph or Me). The molecular geometries of Me₂Sn(S2MoVa), Me₂Sn(S4MoVa) and Me₂Sn(SBoVa) were established by X-ray crystallography and verified using density functional theory calculations. Interestingly, each experimental structure contained two independent but chemically similar molecules in the crystallographic asymmetric unit. The coordination geometry for each molecule was defined by thiolate-sulphur, phenoxide-oxygen and imine-nitrogen atoms derived from a dinegative, tridentate dithiocarbazate ligand with the remaining positions occupied by the methyl-carbon atoms of the organo groups. In each case, the resulting five-coordinate C₂NOS geometry was almost exactly intermediate between ideal trigonal-bipyramidal and square-pyramidal geometries. The cytotoxic activities of the Schiff bases and organotin(IV) compounds were investigated against EJ-28 and RT-112 (bladder), HT29 (colon), U87 and SJ-G2 (glioblastoma), MCF-7 (breast) A2780 (ovarian), H460 (lung), A431 (skin), DU145 (prostate), BE2-C (neuroblastoma) and MIA (pancreatic) cancer cell lines and one normal breast cell line (MCF-10A). Diphenyltin(IV) compounds exhibited greater potency than either the Schiff bases or the respective dimethyltin(IV) compounds. Mechanistic studies on the action of these compounds against bladder cancer cells revealed that they induced the production of reactive oxygen species (ROS). The bladder cancer cells were apoptotic after 24 h post-treatment with the diphenyltin(IV) compounds. The interactions of the organotin(IV) compounds with calf thymus DNA (CT-DNA) were experimentally explored using UV-vis absorption spectroscopy. This study revealed that the organotin(IV) compounds have strong DNA binding affinity, verified via molecular docking simulations, which suggests that these organotin(IV) compounds interact with DNA via groove-binding interactions.

In vitro anti-bacterial and time kill evaluation of binuclear tricyclohexylphosphanesilver(I) dithiocarbamates, {Cy3PAg(S2CNRR')}2

Four binuclear phosphanesilver(I) dithiocarbamates, {cyclohexyl₃PAg(S₂CNRR')}₂ for R = R' = Et (1), CH₂CH₂ (2), CH₂CH₂OH (3) and R = Me, R' = CH₂CH₂OH (4) have been synthesised and characterised by spectroscopy and crystallography, and feature tri-connective, μ₂-bridging dithiocarbamate ligands and distorted tetrahedral geometries based on PS₃ donor sets. The compounds were evaluated for anti-bacterial activity against a total of 12 clinically important pathogens. Based on minimum inhibitory concentration (MIC) and cell viability tests (human embryonic kidney cells, HEK 293), 1-4 are specifically active against Gram-positive bacteria while demonstrating low toxicity; 3 and 4 are active against methicillin resistant S. aureus (MRSA). Across the series, 4 was most effective and was more active than the standard anti-biotic chloramphenicol. Time kill assays reveal 1-4 to exhibit both time- and concentration-dependent pharmacokinetics against susceptible bacteria. Compound 4 demonstrates rapid (within 2 h) bactericidal activity at 1 and 2 × MIC to reach a maximum decrease of 5.2 log₁₀ CFU/mL against S. aureus (MRSA).

Visualizing the coordination-spheres of photoexcited transition metal complexes with ultrafast hard X-rays

The concept of coordination sphere (CS) is central to the rational development of hierarchical molecular assemblies in modern chemistry.

Strong stacking interactions of metal–chelate rings are caused by substantial electrostatic component

Stacking interactions of metal–chelate rings are strong due to very strong electrostatic energy component.

Diethylaminophenyl-based Schiff base Cu(ii) and V(iv) complexes: experimental and theoretical studies and cytotoxicity assays

A combined experimental and theoretical study and cytotoxicity assays of diethylaminophenyl-based Schiff base Cu(ii) and VO(iv) complexes are reported. The Cu(ii) complex shows interesting chelate ring⋯π interactions in the crystal structure.

On the capability of metal–halogen groups to participate in halogen bonds

Halogens in a M–X bond are inhibited from forming a halogen bond but can do so in certain circumstances, with or without a σ-hole.

A new structural motif for cadmium dithiocarbamates: crystal structures and Hirshfeld surface analyses of homoleptic zinc and cadmium morpholine dithiocarbamates

The crystal and molecular structures of two homoleptic morpholine-derived dithiocarbamates of zinc, binuclear {Zn[S2CN(CH2CH2)2O)2]2}2 (1), and cadmium, one-dimensional coordination polymer {Cd[S2CN(CH2CH2)2O)2]2}2 (2), are described. In 1, a centrosymmetric binuclear molecule is found as there are equal numbers of chelating and bidentate bridging dithiocarbamate ligands; weak transannular Zn···S interactions are found within the resultant eight-membered {···SCSZn}2 ring which has the form of a chair. The resultant 4+1 S5 donor set is highly distorted with the geometry tending towards a square-pyramid. By contrast, a square-planar geometry is found in centrosymmetric 2 defined by symmetrically chelating dithiocarbamate ligands. The presence of Cd···S secondary bonding in the crystal of 2 leads to a distorted 4+2 S6 octahedron and a linear coordination polymer, which is unprecedented in the structural chemistry of cadmium dithiocarbamates. The analyses of the Hirshfeld surfaces for 1 and 2 show the dominance of H···H, S···H/H···S and O···H/H···O contacts to the surface, i.e. contributing around 90 and 80%, respectively.

[O-Isopropyl-N-(4-nitrophenyl)thiocarbamato-κS]-(tri-4-tolylphosphine-κP)gold(I)

The synthesis, spectroscopic characterization and X-ray crystal structure of the title compound, (4-tolyl)3PAu[SC(O-i-Pr)=NC6H4NO2-4] (1) are described. Spectroscopy exhibited the expected features confirming the formation of the compound. The molecular structure of 1 confirms the expected linear P–Au–S coordination geometry defined by thiolate-S and phosphane-P atoms. The nearly 7° deviation from linearity is ascribed to the close approach of the imine-bound phenyl group, indicative of a semi-localized Au…π(arene) interaction. The three-dimensional molecular packing is consolidated by methyl- and tolyl-C–H…O(nitro) and tolyl-C–H…π(tolyl) interactions.

Steric control of supramolecular association in structures of Zn(S2COR)2 with N,N′-bis(pyridin-4-ylmethyl)oxalamide

The crystal and molecular structures of the one-dimensional coordination polymer [Zn(S2COEt)2(4LH2)]n (1) and binuclear [Zn(S2COCy)2]2(4LH2) (2) are described, where 4LH2 is N,N′-bis(pyridin-4-ylmethyl)ethanediamide. In 1, the Zn(S2COEt)2 entities are linked by bidentate bridging 4LH2 ligands through the pyridyl-N atoms to generate a twisted supramolecular chain. As a result of monodentate xanthate ligands, the N2S4 donor set defines a distorted tetrahedral coordination geometry and, crucially, allows the participation of the non-coordinating sulfur atoms in supramolecular association. Thus, in the crystal amide-N–H···O(amide) and amide-N–H···S(thione) hydrogen bonds link chains into a three-dimensional architecture. The substitution of the ethyl group in the xanthate ligand with a cyclohexyl group results in very different structural outcomes. In 2, a binuclear molecule is observed with the coordination geometry for zinc being defined by chelating xanthate ligands and a pyridyl-N atom with the NS4 donor set defining a highly distorted geometry. In the molecular packing, amide-N–H···S(thione) hydrogen bonds stabilise a supramolecular chain along the a-axis and these are connected into a three-dimensional arrangement by methylene-C–H···O and methylene-C–H···π(pyridyl) interactions. The relative importance of the specified intermolecular interactions and weaker, contributing contacts has been revealed by an analysis of the calculated Hirshfeld surfaces of 1 and 2.

Evaluation of dispersion type metal···π arene interaction in arylbismuth compounds - an experimental and theoretical study

The dispersion type Bi···π arene interaction is one of the important structural features in the assembly process of arylbismuth compounds. Several triarylbismuth compounds and polymorphs are discussed and compared based on the analysis of single crystal X-ray diffraction data and computational studies. First, the crystal structures of polymorphs of Ph3Bi (1) are described emphasizing on the description of London dispersion type bismuth···π arene interactions and other van der Waals interactions in the solid state and the effect of it on polymorphism. For comparison we have chosen the substituted arylbismuth compounds (C6H4-CH═CH2-4)3Bi (2), (C6H4-OMe-4)3Bi (3), (C6H3-t-Bu2-3,5)3Bi (4) and (C6H3-t-Bu2-3,5)2BiCl (5). The structural analyses revealed that only two of them show London dispersion type bismuth···π arene interactions. One of them is the styryl derivative 2, for which two polymorphs were isolated. Polymorph 2a crystallizes in the orthorhombic space group P212121, while polymorph 2b exhibits the monoclinic space group P21/c. The general structure of 2a is similar to the monoclinic C2/c modification of Ph3Bi (1a), which leads to the formation of zig-zag Bi-arenecentroid ribbons formed as a result of bismuth···π arene interactions and π···π intermolecular contacts. In the crystal structures of the polymorph 2b as well as for 4 bismuth···π arene interactions are not observed, but both compounds revealed C-HPh···π intermolecular contacts, as likewise observed in all of the three described polymorphs of Ph3Bi. For compound 3 intermolecular contacts as a result of coordination of the methoxy group to neighboring bismuth atoms are observed overruling Bi···π arene contacts. Compound 5 shows a combination of donor acceptor Bi···Cl and Bi···π arene interactions, resulting in an intermolecular pincer-type coordination at the bismuth atom. A detailed analysis of three polymorphs of Ph3Bi (1), which were chosen as model systems, at the DFT-D level of theory supported by DLPNO-CCSD(T) calculations reveals how van der Waals interactions between different structural features balance in order to stabilize molecular arrangements present in the crystal structure. Furthermore, the computational results allow to group this class of compounds into the range of heavy main group element compounds which have been characterized as dispersion energy donors in previous work.

Exploring the Topological Landscape Exhibited by Binary Zinc-triad 1,1-dithiolates

The crystal chemistry of the zinc-triad binary 1,1-dithiolates, that is, compounds of xanthate [−S2COR], dithiophosphate [−S2P(OR)2], and dithiocarbamate [−S2CNR2] ligands, is reviewed. Owing to a wide range of coordination modes that can be adopted by 1,1-dithiolate anions, such as monodentate, chelating, μ2-bridging, μ3-bridging, etc., there exists a rich diversity in supramolecular assemblies for these compounds, including examples of zero-, one-, and two-dimensional architectures. While there are similarities in structural motifs across the series of 1,1-dithiolate ligands, specific architectures are sometimes found, depending on the metal centre and/or on the 1,1-dithiolate ligand. Further, an influence of steric bulk upon supramolecular aggregation is apparent. Thus, bulky R groups generally preclude the close approach of molecules in order to reduce steric hindrance and therefore, lead to lower dimensional aggregation patterns. The ligating ability of the 1,1-dithiolate ligands also proves crucial in determining the extent of supramolecular aggregation, in particular for dithiocarbamate species where the relatively greater chelating ability of this ligand reduces the Lewis acidity of the zinc-triad element, which thereby reduces its ability to significantly expand its coordination number. Often, the functionalisation of the organic substituents in the 1,1-dithiolate ligands, for example, by incorporating pyridyl groups, can lead to different supramolecular association patterns. Herein, the diverse assemblies of supramolecular architectures are classified and compared. In all, 27 structurally distinct motifs have been identified.

Investigation of interactions in Lewis pairs between phosphines and boranes by analyzing crystal structures from the Cambridge Structural Database

The interactions between phosphines and boranes in crystal structures have been investigated by analyzing data from the Cambridge Structural Database (CSD). The interactions between phosphines and boranes were classified into three types; two types depend on groups on the boron atom, whereas the third one involves frustrated Lewis pairs (FLPs). The data enabled geometric parameters in structures to be compared with phosphine-borane FLPs with classical Lewis pairs. Most of the crystal structures (78.1%) contain BH₃ as the borane group. In these systems, the boron-phosphorus distance is shorter than systems where the boron atom is surrounded by groups other than hydrogen atoms. The analysis of the CSD data has shown that FLPs have a tendency for the longest boron-phosphorus distance among all phosphine-borane pairs, as well as different other geometrical parameters. The results show that most of the frustrated phosphine-borane pairs found in crystal structures are bridged ones. The minority of non-bridged FLP structures contain, beside phosphorus and boron atoms, other heteroatoms (O, N, S for instance).

Macrocyclic Receptor for Precious Gold, Platinum, or Palladium Coordination Complexes

Two macrocyclic tetralactam receptors are shown to selectively encapsulate anionic, square-planar chloride and bromide coordination complexes of gold(III), platinum(II), and palladium(II). Both receptors have a preorganized structure that is complementary to its precious metal guest. The receptors do not directly ligate the guest metal center but instead provide an array of arene π-electron donors that interact with the electropositive metal and hydrogen-bond donors that interact with the outer electronegative ligands. This unique mode of supramolecular recognition is illustrated by six X-ray crystal structures showing receptor encapsulation of AuCl₄^-, AuBr₄^-, PtCl₄^-2, or Pd₂Cl₆^-2. In organic solution, the 1:1 association constants correlate with specific supramolecular features identified in the solid state. Technical applications using these receptors are envisioned in a wide range of fields that involve precious metals, including mining, recycling, catalysis, nanoscience, and medicine.

Chelated metal ions modulate the strength and geometry of stacking interactions: energies and potential energy surfaces for chelate-chelate stacking

Quantum chemical calculations were performed on model systems of stacking interactions between the acac type chelate rings of nickel, palladium, and platinum. CCSD(T)/CBS calculations showed that chelate-chelate stacking interactions are significantly stronger than chelate-aryl and aryl-aryl stacking interactions. Interaction energy surfaces were calculated at the LC-ωPBE-D3BJ/aug-cc-pVDZ level, which gives energies in good agreement with CCSD(T)/CBS. The stacking of chelates in an antiparallel orientation is stronger than the stacking in a parallel orientation, which is in agreement with the larger number of antiparallel stacked chelates in crystal structures from the Cambridge Structural Database. The strongest antiparallel chelate-chelate stacking interaction is formed between two platinum chelates, with a CCSD(T)/CBS interaction energy of -9.70 kcal mol-1, while the strongest stacking between two palladium chelates and two nickel chelates has CCSD(T)/CBS energies of -9.21 kcal mol-1 and -9.50 kcal mol-1, respectively. The strongest parallel chelate-chelate stacking was found for palladium chelates, with a LC-ωPBE-D3BJ/aug-cc-pVDZ energy of -6.51 kcal mol-1. The geometries of the potential surface minima are not the same for the three metals. The geometries of the minima are governed by electrostatic interactions, which are the ones determining the positions of the energy minima. Electrostatic interactions are governed by different electrostatic potentials above the metals, which are very positive for nickel, slightly positive for palladium, and slightly negative for platinum.

Sulfur(lone-pair)…π interactions with FAD in flavoenzymes

The interactions of π-systems with lone-pairs of electrons are known and have been described in biological systems, involving lone-pairs derived from metals, metalloids, sulfur, oxygen and nitrogen. This study describes a bibliographic survey of the disulfide-bound sulfur(lone-pair) interactions with π-systems residing in the flavin adenine dinucleotide (FAD) cofactor of oxidoreductase enzymes (flavoenzymes). Thus, of the 172 oxidoreductase enzymes evaluated for gamma-S(lone-pair)…π(FAD) interactions, 96 proteins (56%) exhibited these interactions corresponding; 61% of 350 the constituent monomers featured at least one gamma-S(lone-pair)…π(FAD) interaction. Two main points of association between the S(lone-pair) and the isoalloxazine moiety of FAD were identified, namely at the centroid of the bond linking the uracil and pyrazine rings (60%), and the centroid of the uracil ring (37%). Reflecting the nature of the secondary structure in three prominent classes of oxidoreductase enzymes: glutathione disulfide reductases (GR; 21 proteins), trypanothione disulfide reductases (TR, 14) and sulfhydryl oxidases (SOX, 22), the approach of the gamma-S(lone-pair) to the FAD residue was to the si-face of the isoalloxazine ring system, i.e. to the opposite side as the carbonyl residue, for all GR and TR examples, and to the re-face for all SOX examples. Finally, the attractive nature of the gamma-S(lone-pair)…π(FAD) interactions was confirmed qualitatively by an examination of the non-covalent interaction plots.

Crystal structure of {N-(3-ethoxy-2-oxidobenzylidene)-4-fluorobenzohydrazonato-κ3 O,N,O′}dimethyltin(IV), C18H19FN2O3Sn

C18H19FN2O3Sn, monoclinic, C2/c (no. 15), a = 27.1120(3) Å, b = 9.5721(1) Å, c = 13.3072(1) Å, β = 98.271(1)°, V = 3417.55(6) Å3, Z = 8, R gt(F) = 0.016, wR ref(F 2) = 0.043, T = 100(2) K.

Pseudohalide Tectons within the Coordination Sphere of the Uranyl Ion: Experimental and Theoretical Study of C-H···O, C-H···S, and Chalcogenide Noncovalent Interactions

A series of uranyl thiocyanate and selenocyanate of the type [R₄N]₃[UO₂(NCS)₅] (R₄ = ⁿBu₄, Me₃Bz, Et₃Bz), [Ph₄P][UO₂(NCS)₃(NO₃)] and [R₄N]₃[UO₂(NCSe)₅] (R₄ = Me₄, ⁿPr₄, Et₃Bz) have been prepared and structurally characterized. The resulting noncovalent interactions have been examined and compared to other examples in the literature. The nature of these interactions is determined by the cation so that when the alkyl groups are small, chalcogenide···chalcogenide interactions are present, but this "switches off" when R = ⁿPr and charge assisted U═O···H-C and S(e)···H-C hydrogen bonding remain the dominant interaction. Increasing the size of the chain to ⁿBu results in only S···H-C interactions. The spectroscopic implications of these chalcogenide interactions have been explored in the vibrational and photophysical properties of the series [R₄N]₃[UO₂(NCS)₅] (R₄ = Me₄, Et₄, ⁿPr₄, ⁿBu₄, Me₃Bz, Et₃Bz), [R₄N]₃[UO₂(NCSe)₅] (R₄ = Me₄, ⁿPr₄, Et₃Bz) and [Et₄N]₄[UO₂(NCSe)₅][NCSe]. The data suggest that U═O···H-C interactions are weak and do not perturb the uranyl moiety. While the chalcogenide interactions do not influence the photophysical properties, a coupling of the U═O and δ(NCS) or δ(NCSe) vibrational modes is observed in the 77 K solid state emission spectra. A theoretical examination of representative examples of Se···Se, C-H···Se, and C-H···O═U by molecular electrostatic potentials and NBO and AIM methodologies gives a deeper understanding of these weak interactions. C-H···Se are individually weak but C-H···O═U interactions are even weaker, supporting the idea that the -yl oxo's are weak Lewis bases. An Atoms in Molecules study suggests that the chalcogenide interaction is similar to lone pair···π or fluorine···fluorine interactions. An oxidation of the NCS ligands to form [(UO₂)(SO₄)₂(H₂O)₄]·3H₂O was also noted.

Electrophilic-Nucleophilic Dualism of Nickel(II) toward Ni···I Noncovalent Interactions: Semicoordination of Iodine Centers via Electron Belt and Halogen Bonding via σ-Hole

The nitrosoguanidinate complex [Ni{NH═C(NMe₂)NN(O)}₂] (1) was cocrystallized with I₂ and sym-trifluorotriiodobenzene (FIB) to give associates 1·2I₂ and 1·2FIB. Structures of these solid species were studied by XRD followed by topological analysis of the electron density distribution within the framework of Bader's approach (QTAIM) at the M06/DZP-DKH level of theory and Hirshfeld surface analysis. Our results along with inspection of XRD (CCDC) data, accompanied by the theoretical calculations, allowed the identification of three types of Ni···I contacts. The Ni···I semicoordination of the electrophilic nickel(II) center with electron belt of I₂ was observed in 1·2I₂, the metal-involving halogen bonding between the nucleophilic nickel(II)-d_z² center and σ-hole of iodine center was recognized and confirmed theoretically in the structure of [FeNi(CN)₄(IPz)(H₂O)]_n (IPz = 4-N-coordinated 2-I-pyrazine), whereas the arrangement of FIB in 1·2FIB provides a boundary case between the semicoordination and the halogen Ni···I bondings. In 1·2I₂ and 1·2FIB, noncovalent interactions were studied by variable temperature XRD detecting the expansion of noncovalent contacts with preservation of covalent bond lengths upon the temperature increase from 100 to 300 K. The nature and energies of all identified types of the Ni···I noncovalent interactions in the obtained (1·2I₂ and 1·2FIB) and in the previously reported ([FeNi(CN)₄(IPz)(H₂O)]_n, [NiL₂](I₃)₂·2I₂ (L = o-phenylene-bis(dimethylphosphine), [NiL]I₂ (L = 1,4,8,11-tetra-azacyclotetradecane), Ni(en)₂]_n[AgI₂]_2n (en = ethylenediamine), and [NiL](ClO₄) (L = 4-iodo-2-((2-(2-(2-pyridyl)ethylsulfanyl)ethylimino)methyl)-phenolate)) structures were studied theoretically. The estimated strengths of these Ni···I noncovalent contacts vary from 1.6 to 4.1 kcal/mol and, as expected, become weaker on heating. This work is the first emphasizing electrophilic-nucleophilic dualism of any metal center toward noncovalent interactions.

Heteroaryl bismuthines: a novel synthetic concept and metalπ heteroarene interactions

The alkoxide Bi[OCMe₂(2-C₄H₃S)]₃ (1) is formed by the reaction of three equiv. of the alcohol HOCMe₂(2-C₄H₃S) with Bi(O^tBu)₃ and subsequent hydrolysis provides the bismuth oxido cluster [Bi₄O₂{OCMe₂(2-C₄H₃S)}₈] (2). In contrast, the reaction of Bi(O^tBu)₃ and Bi[N(SiMe₃)₂]₃ with the silanols HOSiMe₂(2-C₄H₃X) (X = O, S, Se, and NMe), HOSiMe₂(2-C₄H₂S-5-SiMe₃) and HOSiMe₂(3-C₄H₃S) leads to the formation of tris(heteroaryl)bismuthines Bi(2-C₄H₂X-5-R)₃ [where X = O, R = H (3); X = S, R = H (4); X = S, R = SiMe₃ (5); X = NMe, R = H (6); X = Se, R = H (7)] and Bi(3-C₄H₃S)₃ (8). For the silanols, bismuth-carbon bond formation is observed rather than silanol-alcoholate or silanol-amide exchange. The structures of compounds 1, 2, and 4-7a in the solid state were established by single crystal X-ray diffraction and all compounds except 5 show London dispersion type bismuthπ heteroarene interactions. For the bismuthine Bi(2-C₄H₃Se)₃ (7), two polymorphs were isolated depending on the conditions of crystallization. At 8 °C, polymorph I (7a) crystallizes from an n-hexane solution in the triclinic space group P1[combining macron], whereas polymorph II (7b) crystallizes at 20 °C from a CH₂Cl₂/n-pentane solution in the monoclinic space group P2₁/c. The heteroaryl bismuthines 3 and 4 exhibit 2D network structures as a result of bismuthπ heteroarene interactions, whereas for the pyrrole derivative 6 the dispersion type interactions provide separated dimers.

Crystal structure of (OC-6-13)-diaqua-bis(3,5-di(pyridin-3-yl)-4H-1,2,4-triazol-4-amine-κ1 N)-bis(dicyanamido-κ1 N)zinc(II) tetrahydrate, ZnC28H32N18O6

ZnC28H32N18O6, monoclinic, P21/c (no. 14), a = 10.472(2) Å, b = 21.668(4) Å, c = 8.1282(15) Å, β = 105.763(5)°, V = 1775.0(6) Å3, Z = 2, R gt(F) = 0.0459, wR ref(F 2) = 0.1133, T = 298 K.

Recurrent supramolecular motifs in discrete complexes and coordination polymers based on mercury halides: prevalence of chelate ring stacking and substituent effects

We report the synthesis, X-ray characterization and DFT study of five Hg(ii) complexes with Schiff bases containing a nicotinohydrazide core to explore the formation of chelate-ring π-stacking interactions.

Aurophilicity vs. thiophilicity: directing the crystalline supramolecular arrangement in luminescent gold compounds

The fluorination of thiolate ligands is applied as a tool that allows control of the prevalence of thiophilic (Au–S) interactions over the expected aurophilic contacts in luminescent gold compounds.

Crystal structure of (4,4'-bipyridyl-κN)bis-[N-(2-hydroxy-ethyl)-N-iso-propyl-dithio-carbamato-κ2S,S']zinc(II)-4,4'-bipyridyl (2/1) and its isostructural cadmium(II) analogue

The title structures, [M(C6H12NOS2)2(C10H8N2)]·0.5C10H8N2, for M = Zn, (I), and Cd, (II), feature terminally bound 4,4'-bipyridyl ligands and non-coordinating 4,4'-bi-pyridyl mol-ecules, with the latter disposed about a centre of inversion. The coordination geometry about the metal atom is defined by two non-symmetrically chelating di-thio-carbamate ligands and a pyridyl N atom. The NS4 donor sets are distorted but, approximate to trigonal bipyramidal in each case. In the crystal, hy-droxy-O-H⋯O(hy-droxy) and hy-droxy-O-H⋯N(pyrid-yl) hydrogen bonds between the zinc-containing mol-ecules lead to a supra-molecular layer parallel to (100). The three-dimensional architecture arises as the layers are linked via methine-C-H⋯S, pyridyl-C-H⋯O(hy-droxy) and π-π [inter-centroid distance between coordinated pyridyl rings = 3.6246 (18) Å] inter-actions. Channels along the c-axis direction are occupied by the non-coordinating 4,4'-bipyridine mol-ecules, which are held in place by C-H⋯π(chelate ring) contacts.

New monoclinic form of {O-Ethyl N-(4-nitro-phen-yl)thio-carbamato-κS}(tri-4-tolyl-phosphane-κP)gold(I): crystal structure and Hirshfeld surface analysis

The title phosphanegold(I) thiol-ate compound, [Au(C9H9N2O3S)(C21H21P)], is a second monoclinic polymorph (space group P21/c) that complements a previously reported Cc polymorph [Broker & Tiekink (2008 ▸). Acta Cryst. E64, m1582]. An SP donor set defines an approximately linear geometry about the gold atom in both forms. The key distinguishing feature between the present structure and the previously reported polymorph rests with the relative disposition of the thiol-ate ligand. In the title compound, the orientation is such to place the oxygen atom in close contact with the gold atom [Au⋯O = 2.915 (2) Å], in contrast to the aryl ring in the original polymorph. In the crystal, linear supra-molecular chains along the a-axis direction mediated by C-H⋯π and nitro-O⋯π inter-actions are found. These pack with no directional inter-actions between them. The analysis of the Hirshfeld surfaces for both forms of [Au(C9H9N3O3S)(C21H21P)] indicates quite distinctive inter-action profiles relating to the differences in inter-molecular contacts found in their respective crystals.

Crystal structures of {μ2-N,N'-bis-[(pyridin-3-yl)meth-yl]ethanedi-amide}tetra-kis-(di-methyl-carbamodi-thio-ato)dizinc(II) di-methyl-formamide disolvate and {μ2-N,N'-bis-[(pyridin-3-yl)meth-yl]ethanedi-amide}tetra-kis-(di-n-propyl-carbamodi-thio-ato)dizinc(II)

The title structures, [Zn2(C3H6NS2)4(C14H14N4O2)]·2C3H7NO (I) and [Zn2(C7H14NS2)4(C14H14N4O2)] (II), each feature a bidentate, bridging bipyridyl-type ligand encompassing a di-amide group. In (I), the binuclear compound is disposed about a centre of inversion, leading to an open conformation, while in (II), the complete mol-ecule is completed by the application of a twofold axis of symmetry so that the bridging ligand has a U-shape. In each of (I) and (II), the di-thio-carbamate ligands are chelating with varying degrees of symmetry, so the zinc atom is within an NS4 set approximating a square-pyramid for (I) and a trigonal-bipyramid for (II). The solvent di-methyl-formaide (DMF) mol-ecules in (I) connect to the bridging ligand via amide-N-H⋯O(DMF) and various amide-, DMF-C-H⋯O(amide, DMF) inter-actions. The resultant three-mol-ecule aggregates assemble into a three-dimensional architecture via C-H⋯π(pyridyl, chelate ring) inter-actions. In (II), undulating tapes sustained by amide-N-H⋯O(amide) hydrogen bonding lead to linear supra-molecular chains with alternating mol-ecules lying to either side of the tape; no further directional inter-actions are noted in the crystal.

Bis[N-2-hy-droxy-ethyl,N-methyl-dithio-carbamato-κ2S,S)'-4-{[(pyridin-4-yl-methyl-idene)hydrazinyl-idene}meth-yl]pyridine-κN1)zinc(II): crystal structure and Hirshfeld surface analysis

In the title compound, [Zn(C4H8NOS2)2(C12H10N4)], the ZnII atom exists within a NS4 donor set defined by two chelating di-thio-carbamate ligands and a pyridyl-N atom derived from a terminally bound 4-pyridine-aldazine ligand. The distorted coordination geometry tends towards square-pyramidal with the pyridyl-N atom occupying the apical position. In the crystal, hydroxyl-O-H⋯O(hydrox-yl) and hydroxyl-O-H⋯N(pyrid-yl) hydrogen-bonding give rise to a supra-molecular double-chain along [1-10]; methyl-C-H⋯π(chelate ring) inter-actions help to consolidate the chain. The chains are connected into a three-dimensional architecture via pyridyl-C-H⋯O(hydrox-yl) inter-actions. In addition to the contacts mentioned above, the Hirshfeld surface analysis points to the significance of relatively weak π-π inter-actions between pyridyl rings [inter-centroid distance = 3.901 (3) Å].

Crystallographic and docking (Cathepsins B, K, L and S) studies on bioactive halotelluroxetanes

The molecular structures of the halotelluroxetanes p-MeOC6H4Te(X)[C(=C(H)X′)C(CH2)nO], X=X′=Cl and n=6 (1) and X=Cl, X′=Br and n=5 (4), show similar binuclear aggregates sustained by {· · ·Te–O}2 cores comprising covalent Te–O and secondary Te· · ·O interactions. The resulting C2ClO2(lone-pair) sets define pseudo-octahedral geometries. In each structure, C–X· · ·π(arene) interactions lead to supramolecular layers. Literature studies have shown these and related compounds (i.e. 2: X=X′=Cl and n=5; 3: X=X′=Br and n=5) to inhibit Cathepsins B, K, L and S to varying extents. Molecular docking calculations have been conducted on ligands (i.e. cations derived by removal of the tellurium-bound X atoms) 1′–3′ (note 3′=4′) enabling correlations between affinity for sub-sites and inhibition. The common feature of all docked complexes was the formation of a Te–S covalent bond with cysteine residues, the relative stability of the ligands with an E-configuration and the formation of a C–O· · ·π interaction with the phenyl ring; for 1′ the Te–S covalent bond was weak, a result correlating with its low inhibition profile. At the next level differences are apparent, especially with respect to the interactions formed by the organic-ligand-bound halides. While these atoms do not form specific interactions in Cathepsins B and K, in Cathepsin L, these halides are involved in C–O· · ·X halogen bonds.