Crystal structures of 2,2′-bipyridine adducts of two cadmium O-alkyl dithiocarbonates: rationalisation of disparate coordination geometries based on different crystal packing environments

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.

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.

Estimation of conventional C-Hπ (arene), unconventional C-Hπ (chelate) and C-Hπ (thiocyanate) interactions in hetero-nuclear nickel(ii)-cadmium(ii) complexes with a compartmental Schiff base

Three new heteronuclear nickel(ii)/cadmium(ii) complexes, [(SCN)(Cl)Cd(L)Ni(DMF)₂] (1), [(SCN)(CH₃CO₂)Cd(L)Ni(CH₃OH)₂] (2) and [(SCN)(Cl)Cd(L)Ni(NH₂CH₂CH₂CH₂NH₂)]_n (3) {where H₂L = N,N'-bis(3-ethoxy-salicylidene)propane-1,3-diamine is a N₂O₄ compartmental Schiff base}, have been synthesized and characterized. The structures of the complexes have been confirmed by single crystal X-ray diffraction studies. In each complex, nickel(ii) is placed in the inner N₂O₂ environment and cadmium(ii) is placed in the outer O₄ compartment of the compartmental Schiff base. Furthermore, the importance of unconventional C-Hπ (chelate) interactions in the solid state of both complexes and C-Hπ (thiocyanate) interaction in complex 2 has been described by means of DFT and MEP calculations and characterized using NCI plots. All complexes show photoluminescence at room temperature upon irradiation by ultraviolet light. The lifetimes of excited states are in the range of 2-6 ns.

Mono urotropine adducts of some binary zinc xanthates and dithiocarbamates: solid-state molecular structures and supramolecular self-assembly

The molecular structures of [Zn(S2COR)2(hmta)], R=Et (I) and iPr (II), and [Zn(S2CNRR′)2(hmta)], R=R′=Et (III) and R=iPr, R′=CH2CH2OH (IV), feature chelating 1,1-dithiolate ligands and monodentate hmta molecules; hmta=hexamethylenetetramine. The resulting NS4 donor sets are highly distorted, with tendencies towards square pyramidal. Systematic differences in the structures are related to the greater chelating ability of the dithiocarbamate ligands leading to, e.g., elongated Zn–N bond lengths in III and IV. In the molecular packing, an unusual C–H···π(chelate ring) interaction is noted in III, which is correlated with the close to symmetric Zn–S bond lengths formed by the relevant dithiocarbamate ligand and resultant greater metalloaromatic character of the resulting ZnS2C chelate ring, and to the greater distortion of the coordination geometry compared with literature precedents. A three-dimensional architecture found for IV is sustained by hydroxyl-O-H···O, S and N hydrogen bonding.

Bis[bis(N-2-hydroxyethyl,N-isopropyl-dithiocarbamato)mercury(II)]2: crystal structure and Hirshfeld surface analysis

The presence of both κ2-chelating and μ2,κ2-tridentate bridging dithiocarbamate ligands in centrosymmetric {Hg[S2CN(iPr)CH2CH2OH]2}2 (1) leads to globular aggregates that are linked into a three-dimensional architecture via hydroxyl-O–H···O(hydroxy) hydrogen bonding. The structure contrasts that of Hg[S2CN(CH2CH2OH)2]2 (2; this is a literature structure) in which square planar units are connected into supramolecular chains via Hg···S secondary bonding; chains are connected in the crystal structure by hydroxyl-O–H···O(hydroxy) hydrogen bonding. A Hirshfeld surface analysis on 1 and 2 reveal the influence of O–H···O and Hg···S interactions on the molecular packing as well as the distinctive interactions, such as C–H···S interactions in 1 and C–H···π (HgS2C) contacts in 2. A bibliographic survey shows the different structural motifs observed for 1 and 2 are complimented by an additional five motifs for binary mercury(II) dithiocarbamates revealing a fascinating structural diversity for this class of compound.

Crystal structures of (2,2'-bipyridyl-κ(2) N,N')bis-[N,N-bis-(2-hydroxy-eth-yl)di-thio-carbamato-κ(2) S,S']zinc dihydrate and (2,2'-bipyridyl-κ(2) N,N')bis-[N-(2-hydroxy-eth-yl)-N-iso-propyl-dithio-carbamato-κ(2) S,S']zinc

The common feature of the title compounds, [Zn(C5H10NO2S2)2(C10H8N2)]·2H2O, (I), and [Zn(C6H12NOS2)2(C10H8N2)], (II), is the location of the Zn(II) atoms on a twofold rotation axis. Further, each Zn(II) atom is chelated by two symmetry-equivalent and symmetrically coordinating di-thio-carbamate ligands and a 2,2'-bi-pyridine ligand. The resulting N2S4 coordination geometry is based on a highly distorted octa-hedron in each case. In the mol-ecular packing of (I), supra-molecular ladders mediated by O-H⋯O hydrogen bonding are found whereby the uprights are defined by {⋯HO(water)⋯HO(hy-droxy)⋯} n chains parallel to the a axis and with the rungs defined by 'Zn[S2CN(CH2CH2)2]2'. The water mol-ecules connect the ladders into a supra-molecular layer parallel to the ab plane via water-O-H⋯S and pyridyl-C-H⋯O(water) inter-actions, with the connections between layers being of the type pyridyl-C-H⋯S. In (II), supra-molecular layers parallel to the ab plane are sustained by hy-droxy-O-H⋯S hydrogen bonds with connections between layers being of the type pyridyl-C-H⋯S.

Persistence of C–H⋯π(chelate ring) interactions in the crystal structures of Pd(S2COR)2. The utility of Pd(S2COR)2as precursors for palladium sulphide materials

The influence of C–H⋯π(PdS₂C) interactions in the molecular packing of Pd(S₂COR)₂increases as the steric bulk ofRincreases.

Supramolecular architectures sustained by arene-C–H…π(quasi-chelate ring) interactions in the crystal structures of copper(I) complexes

A review of the crystallographic literature is presented whereby structures featuring a quasi-six-membered chelate ring of the type {CuCl…HNCS} were evaluated for the presence of intermolecular C–H…π(quasi-chelate) interactions. These are shown to stabilise crystal structures leading to zero-, one-, two- and even three-dimensional architectures. Details of these interactions are described and a comparison to analogous interactions formed intramolecularly has been made. The C–H…π(quasi-chelate) interactions in these structures occur in one-third of structures where such contacts can potentially form.

Supra- versus intra-molecular π π interactions in M(S2COCH2Ph)2(dafone) compounds: M = Zn and Cd; dafone = 4,5-diazafluoren-9-one-N,N´

Remarkable differences are observed in the molecular structures of Zn(S2COCH2Ph)2(dafone) (1) and Cd(S2COCH2Ph)2(dafone) (2); where dafone is 4,5-diazafluoren-9-one-N,N′. In 1, an S,O mode of coordination of one of the xanthate ligands is observed, an orientation that facilitates the formation of intramolecular π…π interactions between the benzyl and dafone rings. The second xanthate ligand coordinates in an S,S mode and the dafone ligand is chelating. The resulting N2OS3 donor set defines a distorted octahedral coordination geometry. A similar geometry is found in 2 but based on an N2S4 donor set. Despite the different molecular structures, the global crystal packing patterns for 1 and 2 are almost identical, comprising layers.

Steric control over C=O...C=O interactions in M(S2COR)2(dafone) compounds: M = Zn and Cd; R = Me, Et and iPr; dafone = 4,5-diazafluoren-9-one-N,N′

Crystallography shows that with the smaller xanthate-bound methyl groups in Zn(S2COMe)2(dafone) (1) and Cd(S2COMe)2(dafone) (3) anti-parallel C=O…C=O interactions link molecules into dimers. These are further associated via π—π interactions into a supramolecular chain, and in the case of 3 into a supramolecular two-dimensional array via C—H…S contacts. Increasing the size of the organic residue, i.e. to ethyl and isopropyl in Zn(S2COEt)2(dafone) (2), Cd(S2COEt)2(dafone) (4) and Cd(S2CO-iPr)2(dafone) (5), does not allow for the formation of this supramolecular architecture. Instead, supramolecular chains are sustained by C—H…S and C—H…π(chelate) interactions (the latter exclusively in the case of 5). The presence of recognisable/significant π—π and C—H…S and C—H…π(chelate) interactions is not consistent amongst the series yet only two crystal packing patterns are noted depending on the presence of the C=O…C=O interactions. This observation points to the importance of overall crystal packing considerations of binuclear species in 1 and 3, and mononuclear species in 2, 4 and 5.