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The polymorphic form results from an interplay between global molecular packing and stability of molecular conformation.

Stabilising π[C(O)N(H)NC]⋯π(phenyl) interactions are described.

The electronic & steric influence of the dithiophosphate-R groups mediates the formation of unprecedented supramolecular synthons.

1 : 1 co-crystals formed between 1,4-diiodotetrafluorobenzene and each of the three isomeric n-pyridinealdazines (n = 2, 3 and 4), featuring I⋯N halogen bonding contacts within one-dimensional chains, are described.

In addition to a variety of conventional non-covalent intermolecular interactions such as C–H⋯π (arene), C–H⋯Cl and π(arene)⋯π(chelate-ring) contacts, the molecular packing in the crystal of an organotin dithiocarbamate compound, [SnCl(4-ClC6H4)2{S2CN(i-Pr)2}], exhibits evidence for a C–Cl⋯π(chelate-ring) interaction. These interactions occur via a side-on approach of the chloride atom to the chelate-ring and therefore are characterised as C–Cl(lone-pair)⋯π(chelate-ring) interactions, are shown to be attractive by NCI plots and QTAIM analysis, and are apparent in the calculated Hirshfeld surfaces. Theory suggests the energy of association provided by the C–Cl⋯π(chelate-ring) interactions to be about 3–4 kcal mol−1, a value greater than for analogous C–Cl⋯π(arene) and C–H⋯π(arene) interactions. A survey of the literature for related structures suggests that these interactions are not common. The newly described C–Cl(lone-pair)⋯π(chelate-ring) interactions add to the variety of intermolecular interactions able to be formed by chelate-rings in the supramolecular chemistry of metal complexes.

A systematic analysis of the Cambridge Crystallographic Database has been made for supramolecular architectures sustained by C–I⋯π(chelate ring) interactions where the iodide atom is directed towards the ring centroid, Cg, of the arene ring, i.e. with the angle subtended at the iodide atom, C–I⋯Cg (θ) being ≥160°. The majority of the 181 identified aggregates are one-dimensional chains of varying topology (100 examples) followed by zero-dimensional aggregates (71 examples) with only a small number of two-dimensional arrays (4 examples). The overall likelihood for the formation of these delocalised interactions is around 4%, a number that increases to around 15% when the angle θ restriction is relaxed to 90°. A comparison has been made with the formation of C–X⋯π(chelate ring) interactions for the lower X = bromide, chloride and fluoride congeners. This shows these interactions are more likely to form in the order X = I > Br > Cl ≫ F.

Crystallography shows the universal adoption of supramolecular chains featuring hydroxyl-O–H⋯O(hydroxyl) hydrogen bonding in crystals of (HOCH2CH2)2NC(S)N(H)(C6H4Y-4) for Y = H (1), Me (2), Cl (3) and NO2 (4). However, distinct topologies, i.e. linear (Y = H), helical (Y = Me and Cl) and zig-zag (Y = NO2) are noted with major differences in the pitch of the polymer. Geometry-optimisation, MEP and NPA analyses show a distinct electronic structure for the Y = NO2 derivative, in particular relating to the activation of the aryl ring. An exhaustive analysis of the molecular packing (point-to-point interactions, crystal structure similarity, Hirshfeld surface analysis, NCI and QTAIM, interaction energies and energy frameworks) points to the importance of C–H⋯π(aryl) interactions in stabilising the chains but these have a considerably reduced influence in the crystal with Y = NO2 (4), where π(aryl)⋯π(aryl) interactions are important. The more open arrangement for the linear chain in 1 facilitates the formation of C–H⋯π(aryl) interactions and the more compact arrangements enable the formation of stabilising, intra-chain methylene-C–H⋯S(thione) interactions 2–4. This study highlights the role of second-tier non-covalent interactions in the arrangement of conventional hydrogen bonding interactions.

The Cambridge Crystallographic Database has been searched for the presence of intermolecular C–H⋯π(chelate ring) interactions, known to be stabilising, in the crystals of the first-row transition metal dithiocarbamates, i.e. containing anionic ligands of the type −S2CNR2, R = H, alkyl and aryl. A significant propensity to form C–H⋯π(chelate ring) interactions is noted, especially in crystals of nickel and copper dithiocarbamates. The participating hydrogen atoms are characterised as being near an electronegative atom/substituent encouraging their engagement in this supramolecular synthon. The survey shows that an open, square-planar geometry is not a prerequisite for a C–H⋯π(chelate ring) interaction but, allows, on average, more of these contacts leading to one- and two-dimensional architectures. It is concluded that a search for a C–H⋯π(chelate ring) supramolecular synthon should be included in any detailed analysis of the molecular packing of metal-containing crystals.

Crystal structures of the heavier main group elements in low oxidation states have been evaluated for the presence of supramolecular element(lp)⋯π(arene) interactions that are structure-directing. It is revealed that when present, these interactions lead to zero-dimensional, binuclear aggregates but higher-nuclearity species are sometimes observed, with one-dimensional supramolecular chains of varying topology being prominent. By contrast, two-dimensional aggregation based on element(lp)⋯π(arene) interactions are rare. In summary, interactions of main group metal lone-pairs with aromatic rings are revealed as synthons capable of assembling molecules into supramolecular aggregates.

The crystallography of mono-p-substituted derivatives of 1-(arylamino)-1,2,3-triazole-4-carbohydrazides, 1 (X = H), 2 (F), 3 (Cl) and 4 (Br), and a 2,5-dichloro (5) analogue, shows the molecular structures to be similar. Distinct hydrogen bonding patterns based on N–H⋯N and N–H⋯O are observed in their crystal structures with 1, having two independent molecules comprising the asymmetric unit, displaying one pattern, 2 and 5 another, and 3 and 4 yet another. Geometry optimisation calculations indicate that any conformational differences in the solid state do not persist in the gas-phase and that no influence of the substituents is seen on the geometric parameters. A natural population analysis, for both experimental and optimised structures, shows that the charge on the triazole-N3 atom is at a maximum for 1, as opposed to 2–5, an observation correlated with its distinctive packing based around a supramolecular synthon not seen in the other structures. For the molecules having electronegative substituents, molecular electrostatic potentials show that the energies of the amine-H4n atoms are reduced for 2 and 5, compared to 3 and 4. A further distinction in 2–5 is indicated by the Hirshfeld surface analysis which highlights the importance of π⋯π interactions in 2 and 5, i.e. with the more electronegative substituents. Clearly, there is interplay between various factors but all correlated with the influence of the electronegativity of the substituent(s).

Dimethyl sulphoxide (DMSO) molecules in their all-organic solvates were shown to interact with arene rings of organic molecules via DMSO-O(lone pair)⋯π(arene) or DMSO-S(lone pair)⋯π(arene) interactions in approximately 5–6% of their crystal structures, often in conjunction with conventional hydrogen bonding involving the O(DMSO) atom, resulting in zero-, one- and two-dimensional supramolecular architectures. Zero-, one- and two-dimensional supramolecular architectures were also found to be sustained by parallel SO⋯π(arene) interactions operating in combination with hydrogen bonding.

Supramolecular interwoven double chains are found in two isomeric zinc thiolate complexes which differ in terms of the tautomeric forms of the bridging ligands, i.e. 3-NC5H4CH2N(H)C(O)C(O)N(H)CH2C5H4N-3 or 3-NC5H4CH2NC(OH)C(OH)NCH2C5H4N-3. In each case, the bridging ligands are threaded through 28-membered rings mediated by O–H⋯O hydrogen bonding. Hydrogen bonding interactions between the rings and threading molecules, i.e. O–H⋯Ocarbonyl or O–H⋯Nimine, are dependent on the tautomeric form of the threading molecules.

The molecular structures of all but the R = Et/Y = NO2 derivative of the series of structures [(Ph2P(CH2)4PPh2){AuSC(OR)NC6H4Y-4}2] for R = Me, Et or iPr and Y = H, NO2 or Me, display anti-conformations with the carbonimidothioate ligands external to the dppb (Ph2P(CH2)4PPh2) bridge. In the exceptional structure, the thiolate ligands occupy positions proximate to the dppb bridge, an observation rationalized in terms of the dictates of crystal packing. Aurophilic (Au⋯Au) interactions are not observed in their molecular or in their crystal structures. In the Y = NO2 structures, C–H⋯O interactions dominate the crystal packing leading to chain (R = Me or iPr) and layer (R = Et) motifs. Synthons of the type {Au⋯S}2 dominate the crystal packing, leading to a chain, in one example, i.e. R = Me and Y = H. Similar {Au⋯S}2 synthons potentially appear in all the remaining structures except for R = Et and Y = H, but the Au⋯S distances are too long to be considered significant so that C–H⋯S interactions clearly dominate the crystal packing. With the exception of the layer motif found for the R = Et and Y = NO2 derivative, chain motifs, mediated by {Au⋯S}2, C–H⋯O or C–H⋯S interactions persist in the crystal structures.

Crystallographic analysis shows no significant influence is exerted by the nature of Y upon the molecular parameters of the central O–C(S)–N(H) chromophore in the structures of iPrOC(S)N(H)C6H4-4-Y, for Y = H (1), Cl (2), and Me (3); this is verified by a theoretical study. The crystal structures each feature dimeric aggregates as a result of the uniform formation of the {⋯H–N–CS}2, thioamide, synthon. An analysis of the crystal structures shows that the substitution of the chloride atom in (2) by a methyl group, leading to (3), has a profound influence on the crystal packing owing to the participation of the chloride atom in structure directing C–H⋯Cl interactions that link the dimeric aggregates into a double layer structure. In the structures of (1) and (3), C–H⋯S interactions serve to connect molecules into columnar and layer structures, respectively, with weak C–H⋯O (and π⋯π interactions in (3)) further reinforcing the crystal packing.

The interplay between steric demands of dithiophosphate-bound R groups in Zn(S2P(OR)2)2 on the one hand and the coordination requirements of a variety of di-pyridyl-type bases on the other, is shown to be pivotal in determining supramolecular aggregation patterns in a series of their adducts. Thus, the combination of sterically demanding cyclohexyl groups and the congested trans-1,2-bis(2-pyridyl)ethylene ligand leads to a mononuclear species, but replacing the cyclohexyl by the less bulky isopropyl group allows for dimer formation in the structure of [Zn(S2P(OiPr)2)2(2-NC5H4C(H)C(H)C5H4N-2)0.5]2; a similar motif is found when pyrazine is the bridging ligand. These molecules aggregate in the solid-state to form chains via C–H⋯O interactions. Zig-zag polymers are found when the somewhat less congested 2,2′-dithiopyridine and bis(4-pyridyl)amine ligands are used as the bridges; the hydrogen-bonding functionality in the latter leads to a 2-D motif. Finally, exploiting the curved nature of the 1,3-bis(4-pyridyl)propane ligand leads to the formation of helical chains.

The molecular structures of the isomeric N1,N4-bis((pyridine-n-yl)methylene)-cyclohexane-1,4-diamines, where n = 2 (1), 3 (2) and 4 (3), show the same effective conformation, in particular between the n-pyridine rings and the bridging cyclohexane rings. Theoretical structures of 1–3 are more symmetric and confirm that the pyridine residues are orthogonal to the plane through the four methylene groups of the bridging cyclohexyl groups. Crystal packing in 1–3 is dominated by C–H⋯Npyridine interactions. In 1, these interactions lead to linear chains and, along with π⋯π contacts, give rise to a layer structure. In 2, the C–H⋯Npyridine interactions extend in three dimensions and are complemented by C–H⋯N imine and C–H⋯π contacts. Finally, in 3, the C–H⋯Npyridine interactions lead to layers that are connected by C–H⋯π interactions to give a 3D network. It appears that in the structures of 1–3, the relative disposition of the pyridine and imine groups allows for the participation of the former in intermolecular interactions owing to their accessibility compared with the latter.

A number of supramolecular architectures based on hypervalent Sn⋯Cl interactions are observed in a series of eight R2SnCl2 structures ranging from tetrameric assemblies to a variety of polymeric motifs. The absence of Sn⋯Cl interactions in the crystal lattice of tBu2SnCl2 may be attributed to the bulky size of the tin-bound t-butyl groups that precludes such interactions. The influence of the supramolecular aggregation upon molecular geometry has been investigated using ab initio molecular orbital calculations. These show that invariably more symmetric structures are observed in the absence of hypervalent Sn⋯Cl interactions.

A survey of the supramolecular associations operating in the crystal structures of organomercury 1,1-dithiolates shows that owing to the presence of Hg⋯S interactions, dimeric, 1-, 2- and 3-dimensional architectures are generated. Introducing hydrogen-bonding functionality into the 1,1-dithiolate ligand allows for the formation of both intra- and intermolecular hydrogen bonds as well as Hg⋯S interactions, so that 2- and 3-dimensional architectures are formed that are distinct for each of the two polymorphic forms of MeHg(S2CC5H6NH2-2) and for PhHg(S2CC5H6NH2-2).

Structural analysis reveals the presence of supramolecular chains in a series of eight N-arylamino 1,2,3-triazole esters, which differ only in the nature of the substituent (Y) of the terminal aryl ring. In each of 1 (Y = 4-H), 3 (4-Cl), 4 (4-Br), 5 (4-I) and 6 (4-OMe), the chains are sustained by N–H⋯N hydrogen bonding. In 2 (Y = 4-F) and 8 (Y = 2,5-Cl2), the chains are mediated by alternating N–H⋯N and N–H⋯O hydrogen bonding, whereas in 7 (Y = 4-NO2) the chain is sustained by N–H⋯O hydrogen bonding only. While the differences in the adopted supramolecular motifs are qualitatively correlated with the electronegativity of the Y substituents, no quantitative correlations could be made with the electronic structures of the theoretical gas-phase molecules. Two distinct patterns of crystal packing are observed, with the first of these being based on the inter-digitation of layers, comprised of supramolecular chains and connections of the type C–X⋯π(aryl) between them for 3–5 and 8; only weak off-set edge-to-edge π⋯π interactions were noted in the case of 1. A common feature of the zigzag chains in these crystal structures was a syn-disposition of successive aryl rings along the axis of propagation. The remaining structures adopted three-dimensional architectures where the Y substituents of the anti-disposed aryl rings participated in F⋯H (2) or C–H⋯O (6 and 7) interactions. A detailed analysis of the Hirshfeld surfaces and fingerprint plots for 1–8 enabled a comparison of the intermolecular interactions involved in constructing the disparate supramolecular architectures. In the structures featuring N–H⋯N hydrogen bonding leading to the supramolecular chain, the maximum contribution to the overall crystal packing was less than 20%. This increased to over 25% in the case where there was exclusive N–H⋯O hydrogen bonding in the chain.

The presence of localised C–X⋯π [or C–X⋯π(CC)] interactions are shown to be pivotal in the crystal structures of (5-methyl-1-(4-X-arylamino)-1H-1,2,3-triazol-4-yl)methanol derivatives, X = H (1), F (2) and Cl (3). In the absence of halide (1), molecules aggregate into supramolecular chains via alternating ten-membered {⋯HOC2N}2 and 14-membered {⋯HN2C3O}2 synthons. Molecules assemble into a three-dimensional architecture via edge-to-face C–H⋯π(arene) interactions occurring between the phenyl rings. In the presence of halide (i.e. F (2) and Cl (3) in the 4-position of the phenyl ring), two-dimensional arrays are formed by interconnected ten-membered {⋯HOC2N}2 (as seen in 1) and 24-membered {⋯HO⋯NC2OH⋯N4H}2 hydrogen bonded synthons. The latter arrangement allows for the close approach of halide to the 1,2,3-triazole ring and the formation of C–X⋯π interactions which appear to be particularly significant in the case of Cl (3), as evidenced by systematic changes (i.e. elongation) in the geometric parameters within the five-membered ring. In this series of structures, the presence of C–X⋯π interactions is shown to moderate the supramolecular aggregation based on conventional hydrogen bonding.

Crystal packing patterns for a range of chloroquine derivatives have been investigated. For species where the amine-bound R substituent carries atoms not capable of forming significant hydrogen bonding interactions, i.e. R = methyl (1), n-propyl (2), n-butyl (3), 2-chloroethyl (4), 2-azidoethyl (5), N–H⋯N hydrogen bonding between the amine and pyridine groups predominate leading to supramolecular chains. In species carrying hydroxyl groups, i.e. R = 2-hydroxylethyl (6), 1-butanol (7), and (S)-1-butanol (8), the N–H⋯N interactions are subverted by O–H⋯N and N–H⋯O hydrogen bonding that results in the formation of 2-D arrays, establishing an hierarchy of hydrogen bonding interactions in these systems. Despite the differences in hydrogen bonding, globally, the crystal packing in all structures is similar in that the N–H⋯N mediated supramolecular chains of (1–5) aggregate into layers usually via C–H⋯π, C–Cl⋯π and π⋯π interactions. These layers, as with those formed in (6–8), stack into a 3-D arrangement being consolidated via C–H⋯Cl and π⋯π or C–Cl⋯π interactions.

A survey of tellurium, tin and gold structures containing metal⋯π heteroaromatic interactions has been conducted, and their occurrence correlated with previously described metal⋯π aryl interactions. Metal⋯π heteroaromatic interactions are found for all three metals when the heteroaromatic ring was a pyridine/pyridine-derivative, and these contacts lead usually to 0-D or 1-D aggregates with rare examples of 2-D and 3-D architectures. For each of tellurium and tin, metal⋯π aryl interactions are more likely to form over metal⋯π pyridine interactions, while the reverse is true in the case of gold. These observations are readily correlated with the influence of increasing electron density in the pyridine compared with an aryl ring. In the case of tellurium and tin, for which the metal⋯π interaction involves a metal-based lone pair of electrons being donated to the LUMO of the aryl group, increasing the electron density of the aromatic ring naturally decreases the probability of forming this type of interaction. In the case of gold, where the metal⋯π interaction involves the donation of electron density from the aromatic ring to the gold centre, increasing the electron density of the aromatic ring favours such an interaction. At least for the metals surveyed, metal⋯π interactions are observed in a significant number of their crystal structures, for example up to 6% of all tellurium structures feature Te⋯π aryl interactions as a supramolecular synthon.

Crystallography shows that with the exception of the n = 1 and n = 6 derivatives, molecules of dinuclear Ph3Sn(CH2)nSnPh3, n = 1 to 8, display extended conformations where a pair of triphenyltin moieties are linked by methylene bridges of varying length. Discernable supramolecular aggregation patterns stabilised by C–H⋯π contacts lead to chains and ladders or even 2D arrays in most of the solid-state structures. In all but the n = 1 molecule, with inherent steric hindrance which precludes the adoption of molecular symmetry, symmetry is evident in all of the geometry optimised structures calculated using DFT methods; non-systematic variations in geometric parameters apparent in the experimental structures do not persist in the theoretical structures. The greatest disparity between the experimental and theoretical structures is found for the n = 6 compound, featuring a hexamethylene bridge. The linear conformation calculated in the gas-phase distorts to form a curved molecule to allow the more efficient crystal packing of spherical molecules, as for the spherical n = 1 molecule. In the remaining structures, the global crystal packing is based on the stacking of rod-like molecules.

Au⋯π interactions whereby the electron-rich π-system of C6-aromatic rings interact with gold are shown to exist in the crystal structures of both gold(I) and gold(III) complexes, and have been revealed to occur between neutral/neutral, cationic/cationic, and cationic/anionic systems. Supramolecular aggregation facilitated by Au⋯π interactions leads to the formation of 0-dimensional aggregates, e.g. arising from an interaction between a gold complex and a solvent molecule, loosely associated spherical aggregates, e.g. cooperative interactions between centrosymmetrically related gold complexes, and even extended supramolecular polymeric chains of variable topology (e.g. linear, step ladder, and helical). The described Au⋯π interactions represent a new synthon in structural gold chemistry that should be considered in any complete analysis of their crystal structures.

Co-crystallization experiments conducted between thiocarbamide derivatives, (E)-O-alkyl N-aryl-thiocarbamide, ROC(S)N(H)R′, for R = Me, Et and iPr, and R′ = Ph and PhNO2-4, containing a pharmaceutically active chromophorei.e. –C(S)–N(H)–, and the bipyridine-type molecules, 4,4′-bipyridine, trans-1,2-bis(4-pyridyl)ethene and 1,2-bis(4-pyridyl)ethane, showed the formation of stable 2 : 1 co-crystals, i.e. {[ROC(S)N(H)R′]2(bipyridine-type molecule)}. Novel species were formed by grinding and solvent drop grinding methods, and characterized by powder X-ray diffraction. Five 2 : 1 co-crystals were isolated as single crystals by slow evaporation methods and fully characterized by spectroscopic and X-ray crystallographic methods. Uniformly, trimeric aggregates were formed where each pyridine-nitrogen was connected to an amide-H via a Npyridine⋯H–Namide hydrogen bond. This study shows that the eight-membered {⋯H–N–CS}2 homosynthon found in the parent thiocarbamides is readily disrupted in the presence of bipyridine-type molecules to enable the formation of the stable heterosynthon, {N⋯H–N}.

The structures of R3PAu[SC(OMe)=NR′], for R = Ph, o-tol, m-tol or p-tol, and R′ = Ph, o-tol, m-tol, p-tol or C6H4NO2-4, feature linear P-Au-S coordination geometries with intramolecular Au⋯O or Au⋯π interactions depending on the substitution patterns of the R and/or R′ groups. For R = Ph, intramolecular Au⋯O interactions are observed exclusively but when R = p-tol, intramolecular Au⋯π interactions are found unless precluded by steric crowding, i.e. in the case when R′ = m-tol, or by electronic reasons such as the presence of an electron withdrawing nitro group, i.e. when R′ = C6H4NO2-4. In the latter case, aurophilic interactions (Au⋯Au = 3.0872(4) A) are formed, uniquely amongst the series. The mode of coordination of the thiolate ligands in these complexes, arising from either steric or electronic factors or both, has a profound influence on the supramolecular aggregation patterns operating in their crystal structures. In the solvent-free systems that feature intramolecular Au⋯O interactions, columns of molecules stack so that the thiolate residues interdigitate to a greater or lesser extent leaving the aryl groups of the phosphine ligands facing each other, forming phenyl embraces in the Ph3P species or being connected by C–H⋯π contacts involving methyl-H atoms in the isomeric tolyl3P structures. In structures featuring intramolecular Au⋯π interactions, the methoxy-O atom is more accessible for the formation of C–H⋯O contacts. Finally, in the cases where the nitro substituent is present, at least one of the nitro-O atoms is involved in C–H⋯O intercations. In summary, subtle changes in electronic character and/or steric profile of the phosphine and thiolate ligands are seen to influence, systematically, the crystal packing.

The structure of the 1:1 co-crystal formed between the dicarboxylic acid, 2,2′-dithiodibenzoic acid, and each of the isomeric 3- and 4-pyridinealdazines features a supramolecular zig-zag chain constructed about the O–Hacid⋯Npyridine synthon. By contrast, using the same experimental conditions, only a 2:3 co-crystal could be formed when the isomeric 2-pyridinealdazine was used. Here, a pentamer is found, stabilised by the O–Hacid⋯Npyridine synthon and these associate to form a supramolecular chain via C–H⋯π contacts. Theory shows no significant differences in the basicity of the pyridine-nitrogen atoms leading to the conclusion that it is the steric congestion related to the relative disposition of the 2-pyridine nitrogen that is responsible for the observed behaviour.

A range of supramolecular architectures is found in the title dithiocarbamate salts, each with hydrogen bonding functionality in the form of aτ least one hydroxyl group. A common feature in the crystal packing is the prevalence of charge-assisted O–H⋯S hydrogen bonding. In [NH4][S2CN(CH2CH2OH)2] (1), a 3-D network is found mediated by cooperative O–H⋯S, N–H⋯O and N–H⋯S hydrogen bonding. Reducing the hydrogen bonding functionality by replacing the ammonium cation in (1) by the 4-aza-1-azoniabicyclo(2.2.2)octanium cation to give [DABCO-H][S2CN(CH2CH2OH)2] (2), results in a 2-D array. Further reduction of the hydrogen bonding functionality, this time by substituting a CH2CH2OH with an alkyl group to give [DABCO-H][S2CN(CH2CH2OH)CH3] (3) and [DABCO-H][S2CN(CH2CH2OH)CH2CH3] (4) allows for the formation of 1-D supramolecular chains. The introduction of alkali metal cations rather than protic cations removes the possibility of the hydroxyl-O participating in hydrogen bonding interactions as these now coordinate the alkali metal. In the sodium trihydrate, Na[S2CN(CH2CH2OH)2]·3H2O (5), O–H⋯O hydrogen bonds are found along with charge-assisted O–H⋯S contacts so that a 3-D network results. Substituting a CH2CH2OH group with a n-propyl group gives Na[S2CN(CH2CH2OH)CH2CH2CH3]·2H2O (6) and yields a 2-D array. For the anhydrous K[S2CN(CH2CH2OH)2] (7) and Cs[S2CN(CH2CH2OH)2] (8) salts, the crystal packing is dominated by charge-assisted O–H⋯S hydrogen bonding giving 3-D network structures. The systematic analysis of the crystal packing patterns of these salts reveals the importance of charge-assisted O–H⋯S hydrogen bonding in stabilising these crystal structures.

The results of crystallographic analyses on a series of 1 ∶ 1 and 2 ∶ 1 co-crystals formed between 2,2′-dithiodibenzoic acid (DTBA) and each of 4,4′-bipyridine, trans-1,2-bis(4-pyridyl)ethene and 1,2-bis(4-pyridyl)ethane are described. Neutral molecules connected via O–H⋯N hydrogen-bonds leading to chains are found in the 1 ∶ 1 co-crystals. The intervention of a lattice water in a pseudo-polymorph of DTBA ∶ 1,2-bis(4-pyridyl)ethane consolidates chains into a 2-D array. Proton transfer occurs in the 2 ∶ 1 co-crystals so that the predominant motifs are chains of DTBA anions connected via charge-assisted O–H⋯O− interactions. In the co-crystal formed between 2(DTBA) ∶ 4,4′-bipyridine, characterised as a monohydrate, layers comprising DTBA anions are interspersed with layers of bipyridinium cations connected by water molecules. In the 2(DTBA) ∶ trans-1,2-bis(4-pyridyl)ethene and 2(DTBA) ∶ 1,2-bis(4-pyridyl)ethane co-crystals, the layers of DTBA anions are connected via O–H⋯O hydrogen-bonds and define columns in which are threaded chains of bipyridinium cations connected via N–H⋯N+ hydrogen-bonding. Finally, in the pseudopolymorph, 2(DTBA) ∶ 1,2-bis(4-pyridyl)ethane.EtOH, layers of anions are bridged by bipyridinium cations so that rectangular columns are defined and in which the solvent ethanol molecules reside.

Supramolecular association operating in the crystal structures of organo-phosphorus, -arsenic, -antimony and -bismuth 1,1-dithiolate compounds is surveyed with the purpose of delineating the factors that dictate the formation of the resultant range of aggregates. Primary considerations for the formation of secondary M⋯S interactions relate to the Lewis acidity of the central atom that can be moderated by i) the nature of the metal atom itself, e.g. the Lewis acidity of P < As < Sb < Bi, ii) the number of metal-bound organic substituents, e.g. the Lewis acidity of R2M < RM, and iii) the coordination potential of the 1,1-dithiolate ligand, e.g. the Lewis acidity of M(S2CNR2) < M(S2COR). Another vital factor is the steric profile of the metal- and/or ligand-bound R groups, i.e. when R is large, M⋯S interactions are precluded. When M⋯S interactions are absent, for whatever reason, the crystal packing is invariably dominated by C–H⋯S interactions that usually lead to chain motifs.

Structural investigations, i.e. solid-state (X-ray), solution (1H NMR) and gas-phase (theoretical), on molecules with the general formula MeOC(S)N(H)C6H4-4-Y: Y = H (1), NO2 (2), C(O)Me (3), Cl (4) have shown a general preference for the adoption of an E-conformation about the central C–N bond. Such a conformation allows for the formation of a dimeric hydrogen-bonded {⋯H–N–CS}2 synthon as the building block. In the cases of 1–3, additional C–H⋯O interactions give rise to the formation of tapes of varying topology. A theoretical analysis shows that the preference for the E-conformation is about the same as the crystal packing stabilisation energy and consistent with this, the compound with Y = C(O)OMe, (5), adopts a Z-conformation in the solid-state that facilitates the formation of N–H⋯O, C–H⋯O and C–H⋯S interactions, leading to a layer structure. Global crystal packing considerations are shown to be imperative in dictating the conformational form of molecules 1–5.

New structural data for molecules of the general formula Sb(S2CNR2)3, with both non-sterically and sterically demanding R groups, complement literature data and allow an assessment of factors dictating supramolecular association. With relatively small R substituents, dimer formation via Sb⋯S secondary interactions is observed. With bulky R groups, Sb⋯S interactions are not possible owing to steric hindrance and C–H⋯S hydrogen-bonding predominates instead, again leading to dimers. In cases where R carries hydrogen-bonding functionality, both Sb⋯S and O–H⋯O co-exist when R is small but Sb⋯S secondary bonding is switched off when R becomes larger. The conclusion of the study is that remote R substituents in molecules of this type are able to dictate modes of supramolecular association, i.e. Sb⋯S versus C–H⋯S, and that the resultant formation of loosely associated dimers facilitates efficient crystal packing.

A series of Zn(S2P(OR)2)2, R = iPr and Cy, adducts with bridging bipyridine ligands, i.e. 4,4′-bipyridine, trans-1,2-bis(4-pyridyl)ethylene and 1,2-bis(4-pyridyl)ethane have been investigated. The topology of the polymeric structures, i.e. zig-zag versus straight chain, can be controlled by the nature of the bridging bipyridine ligand in the case of adducts formed by Zn(S2P(OCy)2)2, an effect that can be traced to the steric bulk of the cyclohexyl groups. Polymer formation is precluded in the case of the adduct formed between Zn(S2P(OCy)2)2 and 4,4′bipyridine, again a result that is directly ascribed to the steric bulk of the thiolate residue.

A series of 1∶1 adducts formed between Cd(S2P(OiPr)2)2 and the bifunctional ligands 4,4′-bipyridine (1), trans-1,2-bis(4-pyridyl)ethylene (2), 1,2-bis(4-pyridyl)ethane (3), trans-1,2-bis(2-pyridyl)ethylene (4), 1,2-bis(4-pyridyl)propane (5) and 4,4′-dipyridylsulfide (6) demonstrate variable polymer topology (linear, zigzag and arched) and cadmium atom coordination geometry (cis- and trans-N2S4) depending on the nature of the bridging ligand and steric influences of the ligands. Increasing the steric bulk of the Lewis acid, to Cd(S2P(OCy)2)2, results in comparable topologies with bipyridine ligands 1, 2, and 4 but, precludes polymer formation in the adduct formed with 5, a dimer being formed instead.

A survey of the fascinating structural chemistry of the zinc-triad 1,1-dithiolates is presented. A total of twelve distinct structural motifs are delineated ranging from monomeric, dimeric, tetrameric, linear polymeric, layer to 3-dimensional network architectures. Such diversity arises from the prevalent secondary bonding interactions, i.e. A⋯S, operating in the solid state. While the variation in structure suggests that the control of secondary interactions is difficult, a possible design tool for crystal engineering is identified, namely by moderating the steric profile of thiolate-bound organic substituents, at least for the systems described herein.

The structure of Zn(S2COnPr)2 features [–Zn–S–C–S–]4 16-membered rings that share two corners with adjacent rings leading to the formation of a chain. This contrasts the situation in closely related Zn(S2COiPr)2, which displays isolated 16-membered rings, and in Zn(S2COEt)2, which adopts a layer structure owing to all corners of the 16-membered rings being shared. If the isolated 16-membered ring is considered as a paving stone, a description of the Zn(S2COR)2 structures ensues where the pavers in R = iPr are connected into a chain for R = nPr and finally into a 2-D architecture (e.g. path) for R = Et, demonstrating steric control over molecular aggregation.

A common feature of the solid state structures of [(AuSC6H4{C(O)Y}-2)2(μ-dppf)], where dppf is bis(diphenylphosphine)ferrocene, and Y = OH (1), NH2 (2) and N(H)Me (3) is the formation of a chain motif. Association between the molecules is found to be highly dependent on the nature of Y so that in 1 only hydrogen bonding between molecules is observed. In 2, both hydrogen bonding and aurophilic interactions are found. By contrast, in 3 only aurophilic interactions contribute to the formation of the chain. These results are consistent with a similar energy of stabilisation and structure-directing propensity for the hydrogen bonding and aurophilic association operating in these systems.

The crystal and molecular structures of [Au2(2-Hmba)2(-PPh2(CH2)2Ph2P)] (1) and its 1 : 2 adduct with DMSO (1.2DMSO) are reported. In 1, a two-dimensional structure is found mediated, in part, by carboxylic acid dimer formation within the layers. In the di-solvate, these functionalities are not available as they are involved in hydrogen-bonding contacts to DMSO. Nevertheless, a two-dimensional structure is also formed showing that carboxylic acid dimer formation is not pivotal in determining the crystal structure in these systems