The solvent-templating effect as the driving factor that influences the formation of crystalline materials based on the stacking of metallocycles

A series of recrystallisations of a 1 : 1 CuCl2 : L (L = 1,4-bis[(2-methylimidazol-1-yl)methyl]benzene) mixture from a variety of common solvents has been undertaken in order to investigate the effect of solvent templation on the resulting crystal forms. Single crystal X-ray diffraction analysis of eight new solvates of [CuCl2L]n reveals the solvent dependent formation of either a discrete dinuclear metallocycle or a one-dimensional coordination polymer. Conformational flexibility of both the ligand and the metal-ligand bonds results in the ability of these compounds to form a variety of structures. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.</p

Water-assisted self-assembly of harmonic single and triple helices in a polymeric coordination complex

A novel two-dimensional coordination polymer containing infinite, coherently pitched single and triple helical motifs is formed by the self-assembly of Cd2+, succinate, water and a bipyridyl ligand. © The Royal Society of Chemistry 2005.</p

Enclathration of morpholinium cations by Dianin's compound: Salt formation by partial host-to-guest proton transfer

In spite of partial deprotonation upon inclusion of morpholine, Dianin's compound maintains its well-known clathrate structure in the solid state. © The Royal Society of Chemistry 2005.</p

A discrete metallocyclic complex that retains its solvent-templated channel structure on guest removal to yield a porous, gas sorbing material

A discrete rectangular metal-organic complex that stacks to form one-dimensional channels filled with acetonitrile solvent molecules is described. Removal of the solvent under relatively mild conditions proceeds via a single-crystal to single-crystal transformation that leaves the host lattice unaltered. These findings proffer a design strategy for porous materials based on the simple principle that rigid molecular rings cannot pack efficiently and would thus favor the inclusion of guest species whenever possible. Upon guest removal, an efficiently packed new phase can then only be achieved by means of bond cleavage. Thus, achieving crystal porosity by maintaining robust metal-ligand coordination bonds in such discrete cyclic systems directly parallels the strategy employed for MOFs. Copyright © 2005 American Chemical Society.</p

Guest-induced conformational switching in a single crystal

Without destruction of monocrystallinity: The conformational switching of a dinuclear metal complex between four distinct states (see picture) occurs without destroying the single crystal. This observation implies a substantial degree of cooperativity between host molecules during guest uptake, release, or exchange. (Figure Presented). © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.</p

Permeability of a seemingly nonporous crystal formed by a discrete metallocyclic complex

We describe the structure and permeability of a crystalline material that appears to be nonporous in a conventional sense. The material is initially formed as a solvate, and removal of the solvent molecules under relatively mild conditions proceeds via a single-crystal to single-crystal transformation, leaving the host structure intact. Although discrete unoccupied voids of 108 Å3 are present in the structure, it is not possible to map open channels that represent an intuitive pathway for guest diffusion. Despite the apparent absence of pores, the material is permeable to a variety of gases including H2, O2, N2, CO, CH4, CO2, and I2. These findings show that porosity in crystalline systems cannot always be rationalized by considering the static structures and that as-yet unknown dynamic and cooperative mechanisms prevail by which porosity can be induced. Copyright © 2006 American Chemical Society.</p

Breaking the trigonal host packing motif of Dianin's compound

Crystallisation of Dianin's compound (DC) together with two organic amines (piperazine and piperidine) produces co-crystals of 2:1 DC-piperazine and 1:1 DC-piperidine, respectively. The structures of these adducts contrast sharply with that of the well-known clathrate structure of DC in which organic guests are generally included in ratios of 3:1 or 6:1 DC-guest. © The Royal Society of Chemistry 2009.</p

Polymorphism of pure p-tert-butylcalix[4]arene: Subtle thermally-induced modifications

A low-density polymorph of the well-known host compound p-tert-butylcalix[4]arene undergoes subtle structural changes when heated and cooled. © 2004 Royal Society of Chemistry.</p

Co-crystallization of ionic and neutral supramolecular motifs derived from identical components

The concept of co-crystallization usually applies to the coexistence of two or more different types of molecule in the same crystal, but at a higher level of complexity it is possible to define a parallel concept where a crystal is composed of two or more recognizably different supramolecular assemblies. We describe the structure of an adduct formed between Dianin's compound and ethylene diamine. This structure consists of two recognizably different supramolecular assemblies of these components. Furthermore, these two forms have each previously been observed to exist in isolation. Therefore, it is reasonable to make the comparison with conventional co-crystals where two or more compounds that can exist separately form a crystalline adduct (often termed a "molecular complex"). © 2009 American Chemical Society.</p

Diffusion of water in a nonporous hydrophobic crystal

Burrowing water: The apohost phase of a substituted hydrophobic calixarene, grown by sublimation, forms lattice voids but not channels. Exposure of the crystals to liquid water results in a single-crystal-to-single-crystal phase transformation during which water molecules become embedded in the lattice voids (see picture); thus the classical view of diffusion might not be appropriate at the atomic scale. (Chemical Equation Presented) © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.</p