Supramolecular Solids Research Articles

Co-crystallization of a Versatile Building Block Benzoguanamine with Two Flexible Cyclohexanedicarboxylic Acids

Co-crystallization of a versatile building module benzoguanamine (bga) with two flexible cyclohexanedicarboxylic acids, 1,4-cyclohexanedicarboxylic acids (1,4-chdcH2) and 1,3-cyclohexanedicarboxylic acid (1,3-chdcH2) affords two 3-D supramolecular solids of (bga)·(1,4-chdcH2)0.5 (1), and (bga)3·(1,4-chdcH2)·(H2O)2 (2). The supramolecular architectures of the two complexes are predominantly hydrogen bonded via N–H⋯N base pairs, in which adjacent bga molecules form (bga)∞ ribbons via pairs of N–H⋯N hydrogen bonds (R22(8) synthon). Typical acid-base R22 (8) synthons consisting of a nitrogen and amine group of L and carboxylic acid groups featuring N–H⋯O and O–H⋯N hydrogen bonds are also observed in the two complexes. The presence of water molecules makes the network of 2 quite complicated, and a hydrogen-bonded [(1,3-chdcH2)·(H2O)2]∞ chain is also observed. Two co-crystals of benzoguanamine (bga) with two flexible cyclohexanedicarboxylic acids 1,4-cyclohexanedicarboxylic acids (1,4-chdcH2) and 1,3-cyclohexanedicarboxylic acid (1,3-chdcH2) have been obtained and characterized by X-ray crystallography. Two typical R22 (8) synthons consisted by N–H⋯N, N–H⋯O and O–H⋯N hydrogen bonding interactions are observed in the two complexes, leading to two 3-D supramolecular architectures.

Solid-state inclusion of C60 and C70 in a co-polymer induced by metal–ligand coordination of a Zn–porphyrin cage with a bis-pyridyl perylene derivative

We have conducted X-ray characterization of two unprecedented supramolecular solids involving three different components: a suitable Zn(ii)–bisporphyrin cage, a bis-pyridyl perylene derivative and a fullerene.

One pot synthesis, structure and magnetic property of a pseudo-interpenetrated 2D copper framework based on coordinated 1,1′-biphenyl-3,3′,5,5′-tetracarboxylate and synthon

A mixture of 1,1′-biphenyl-3,3′,5,5′-tetracarboxylate acid (abbreviated as H4bpta), 4,4′-bipyridine (abbreviated as 4,4′-bipy), and CuCl2·2H2O generates co-crystallization supramolecular solids [Cu2(cis-H2bpta)2(4,4′-bipy)2]n·nH4bpta·2nH2O (I) under hydrothermal condition and form of partly deprotonated cis-H2bpta2− firstly emerges in this work. Crystallographically, a 1:1 co-crystal is formed by co-crystallization of [Cu2(cis-H2bpta)2(4,4′-bipy)2] and H4bpta in self-assembled process. Structurally, the compound (I) exhibits two-dimensional (2D) double-layered nets with a pseudo-interpenetrated skeleton, one layer is characteristic of metal-organic moiety linked via cis-H2bpta2− and 4,4′-bipy spaces, and the other formed by O–H···O H-bonds presented in neutral H4bpta ligands. Interestingly, its mechanically interlocked structure is formed by hydrogen bonds, which results in an interesting interweaving framework with a new (3,4,5)-connected topological structure. Magnetic couplings between adjacent Cu(II) centers are mediated through double syn-syn carboxylate bridges. Magnetic susceptibility measurement indicates that (I) exhibits a dinuclear Cu(II) behavior with antiferromagnetic coupling (J = −35.69(1) cm−1).

Solution and Mechanochemical Syntheses of Two Novel Cocrystals: Ligand Length Modulated Interpenetration of Hydrogen-Bonded 2D 63-hcb Networks Based on a Robust Trimeric Heterosynthon

Cocrystallization of a versatile organic tecton, 3,3′,5,5′-tetramethyl-4,4′-bipyrazole (tmbpz), with aliphatic dicarboxylic acid suberic acid (H2sub) and sebacic acid (H2seb) generates two supramolecular solids [(tmbpz)2·(H2sub)] (1) and [(tmbpz)2·(H2seb)] (2). In the present case, both cocrystals could be obtained from either solution evaporation or mechanochemical solid-state reaction. Single-crystal structural analyses reveal that the 1 and 2 are 4-fold and 5-fold 2D → 2D parallel interpenetrated 63-hcb networks, respectively. The substantial dissimilarities in the degree of interpenetration are modulated by the different lengths of dicarboxylic acids. The thermal stabilities and photoluminescence behaviors of them were also discussed.

Ruthenium(II) complexes of meso-tetrakis(4-cyanophenyl)porphyrin

Abstract A novel synthesis is presented for the meso -tetrakis(4-cyanophenyl)porphyrin complex Ru(T- p CN- P P)(CO)(H 2 O), the first Ru complex with this long-known porphyrin; compared to standard methods reported for other porphyrin analogues via Ru 3 (CO) 12 , extra steps involving addition of pyridine (Py) and its subsequent removal as [HPy + ]Cl − are required. The Py breaks down coordination polymers (as yet uncharacterized) formed via the peripheral p -cyanophenyl moiety; these materials may offer potential as porphyrin-based supramolecular solids. Removal of the CO by photolysis in MeCN solution generates Ru(T- p CN- P P)(MeCN) 2 , but attempts to make the bis(thiol) analogues from this precursor were unsuccessful, again due to formation of polymeric species.

Mechanochemical synthesis of a fluorenone-based metal organic framework with polarized fluorescence: an experimental and computational study

The regular assembly of organic chromophores into ordered supramolecular solids has received much attention for developing high-performance luminescent materials. Herein, a fluorenone-containing dicarboxylate (FDC) has been organized into a metal organic framework (MOF) with zinc as the metal cation by a facile mechanochemical synthesis method. The obtained Zn–FDC MOF features a pillared structure, in which the fluorenone chromophore units exhibit a highly ordered arrangement. Compared with the pristine FDC sample, the Zn–FDC MOF presents blue-shifted emission, as well as enhanced photoluminescence quantum yield and fluorescence lifetime, demonstrating the ordered arrangement of the FDC within the MOF is beneficial for the improvement of the photo-related properties of the organic chromophore. Moreover, the Zn–FDC MOF film exhibits well-defined polarized photoemission with a polarized anisotropy of 0.10–0.15. Periodic density functional theoretical (DFT) calculations illustrate that no energy/electronic transfer occurs between the chromophore and the metal cation, and the valence electrons localized in the FDC are confined effectively due to the energy blocking action of the metal cations. Combining experimental and theoretical studies on the luminescent MOF system, this work not only gives a rapid and environmentally friendly way to prepare a highly ordered inorganic–organic hybrid system with improved fluorescence properties, but also provides a deep understanding of the electronic structure of the 2D pillared MOF. It is expected that the Zn–FDC MOF can be potentially applied as a polarized fluorescence material.

Inclusion of Cl− or Br− anions within host framework formed by second-sphere interactions

In this study, we have deliberately utilized the second-sphere coordination approach into the construction of supramolecular inclusion solids Cl ⊂ [H2L1]·[InCl4] (Crystal I) and Br ⊂ [H2L1]·[TeBr6] (Crystal II). The chloride or bromine anions can be encapsulated inside the host assemblies formed by the diamine molecule (4,6-dimethyl-1,3-phenylene) bis(N,N-dibenzylmethane) (L1) and the metal complexes ([InCl4]− and [TeBr6]2−) via second-sphere interactions. The inclusion complexes have been structurally characterized by X-ray crystallography, indicating that weak C–H···Cl and C–H···Br hydrogen bonding synthons play a significant role in the construction of host framework. 2-D networks are formed in both complexes by the interconnection of 1-D networks through the multiple weak hydrogen bonding interactions with [InCl4]− or [TeBr6]2−. The guest Cl− or Br− anions are encapsulated inside the host cages through N–H···Cl hydrogen bonds. The inclusion selectively was studied for the two host assemblies.

Structure and inclusion behaviour of five supramolecular inclusion solids constructed from flexible organic layers with [Fe(CN)6]3– as pillars by second-sphere coordination

In the paper, a series of new pillar-layered supramolecular complexes have been built up through second-sphere coordination. Three N,N,N′,N′-tetrabenzyl diamine ligands [N,N,N′,N′-tetrabenzyl-ethylenediamine (L1), N,N,N′,N′-tetrabenzyl-2-butyne-1,4-diamine (L2) and N,N,N′,N′-tetrabenzyl-(p-xylylene)-diamine (L3)] were synthesised, and can react with [Fe(CN)6]3 via second-sphere coordination, yielding pillar-layered supramolecular complexes, [H2L1]0.5·[Fe(CN)6]0.5 ⊃ 0.5H3O·1.5H2O (Crystal 1), [H2L2]0.25·[Fe(CN)6]0.25 ⊃ 0.5H3O·0.5H2O (Crystal 2) and [H2L3]·[Fe(CN)6] ⊃ Cl·ethylene glycol·H2O (Crystal 3). The 3D networks are organic layers formed by the self-assembly of the ligands through extensive hydrogen-bonding interactions (π…π stacking or C–H…π interactions) and further interconnected by [Fe(CN)6]3 − in a pillar fashion, constructing into pillar-layered networks with channels accessible to various guest molecules. The inclusion property of [H2L1]·[Fe(CN)6] was studied; varieties of guest molecules, such as ethanol and tetrahydrofuran, can be included in the framework and lead to the formation of different inclusion complexes [H2L1]·[Fe(CN)6] ⊃ (guest) n (crystal 1, 4–5).

Inclusion of an anion guest within a molecular host formed by (4,6-dimethyl-1,3-phenylene)bis( N , N -dibenzylmethane) and [CuCl4]2−/[TeCl6]2− through second-sphere coordination

In this work, we have utilized the second-sphere coordination approach toward the construction of supramolecular inclusion solids Cl · 2H2O ⊂ [H2L1]0.5 · [CuCl4]0.5 (Crystal 1) and Cl ⊂ [H2L1] · [TeCl6]0.5 (Crystal 2). The chloride anions can be encapsulated inside the host assemblies formed by the diamine molecule (4,6-dimethyl-1,3-phenylene)bis(N,N-dibenzylmethane) (L1) and the metal complexes ([CuCl4]2− and [TeCl6]2−) via second-sphere coordination. The complexes have been structurally characterized by X-ray crystallography, indicating that weak C–H ··· Cl hydrogen-bonding synthons play a significant role in the construction of second-sphere coordination complexes. 2-D networks are formed in both complexes by the interconnection of 1-D networks through multiple C–H ··· Cl hydrogen-bonding interactions with [CuCl4]2− and [TeCl6]2−. The guest chlorides are encapsulated inside the host cages through N–H ··· Cl hydrogen bonds.

An all-organic steroid–D–π-A modular design drives ferroelectricity in supramolecular solids and nano-architectures at RT

Confluence of a modular design approach and self-assembly with a 'steroid-D-π-A' module generates spontaneous polarization in solids and for the first time in nano-architectures constituted from organogels, at room temperature (RT).

Hydrogen bonded binary molecular adducts derived from exobidentate N-donor ligand with dicarboxylic acids: Acid⋯imidazole hydrogen-bonding interactions in neutral and ionic heterosynthons

Four new binary molecular compounds between a flexible exobidentate N-heterocycle and a series of dicarboxylic acids have been synthesized. The N-donor 1,4-bis(imidazol-1-ylmethyl)benzene (bix) was reacted with flexible and rigid dicarboxylic acids viz., cyclohexane-1,4-dicarboxylic acid (H 2chdc), naphthalene-1,4-dicarboxylic acid (H 2npdc) and 1H-pyrazole-3,5-dicarboxylic acid (H 2pzdc), generating four binary molecular complexes. X-ray crystallographic investigation of the molecular adducts revealed the primary intermolecular interactions carboxylic acid⋯amine (via O–H⋯N) as well as carboxylate⋯protonated amine (via N–H +⋯O −) within the binary compounds, generating layered and two-dimensional sheet type H-bonded networks involving secondary weak interactions (C–H⋯O) including the solvent of crystallization. Depending on the differences in p K a values of the selected base/acid (Δp K a), diverse H-bonded supramolecular assemblies could be premeditated. This study demonstrates the H-bonding interactions between imidazole/imidazolium cation and carboxylic acid/carboxylate anion in providing sufficient driving force for the directed assembly of binary molecular complexes. In the two-component solid form of hetero synthons involving bix and dicarboxylic acid, only H 2chdc exist as cocrystal with bix, while all the other three compounds crystallized exclusively as salt, in agreement with the Δp K a values predicted for the formation of salts/cocrystals from the base and acid used in the synthesis of supramolecular solids.

Supramolecular inclusion of a pillared double-layered host by an anion-directed second-sphere coordination

In this paper, we have illustrated the utilisation of a second-sphere coordination approach to construct supramolecular inclusion solids with varieties of guest molecules. A flexible molecule N,N,N′,N′-tetra-p-methylbenzyl-ethylenediamine (L1) bearing doubly protonated H-bond donors was designed, capable of forming N–H…Cl hydrogen bonds with a crystallographically unique chloride anion, to construct an anion-directed ligand. The pillared double-layered host framework was constructed by an anion-directed ligand and primary coordination sphere [CoCl4]2 − through weak C–H…Cl hydrogen-bonding interactions. A variety of guest molecules, such as p-anisaldehyde, 1,4-dimethoxy-2,5-bis(methoxymethyl)benzene, can be included, leading to the formation of novel supramolecular inclusion solids: [L1]·4[H]+·[CoCl4]2 − ·2Cl− ·1.5[C8H8O2]·0.25[CH3OH] (1) and [L1]·4[H]+·[CoCl4]2 − ·2Cl− ·1.5[C12H20O4]·0.5[CH3OH] (2). We have presented herein the utilisation of a second-sphere coordination approach to construct supramolecular inclusion solids with a variety of guest molecules. A novel type of a pillared double-layered host framework was constructed by a second-sphere coordination between the anion-directed ligand (L1 = N,N,N′,N′-tetra-p-methylbenzyl-ethylenediamine) and [CoCl4]2 − through weak C–H…Cl hydrogen-bonding interaction, and a variety of guest molecules, such as p-anisaldehyde, 1,4-dimethoxy-2,5-bis(methoxymethyl)benzene, can be included, leading to the formation of supramolecular inclusion solids: [L1]·4[H]+·[CoCl4]2 − ·2Cl− ·1.5[C8H8O2]·0.25[CH3OH] (1) and [L1]·4[H]+·[CoCl4]2 − ·2Cl− ·1.5[C12H20O4]·0.5[CH3OH] (2)

Silver(I) coordination polymers self-assembled through methanolysis of pyrazinecarbonitrile: Structure and photoluminescence

Abstract New supramolecular solids whose topologies depend on the counteranion, [Ag(MPCI)(CF3CO2)] (1) and [Ag2(MPCI)2(CH3OH)(CF3SO3)]CF3SO3 (2), have been prepared by the self-assembly of AgX ( X = CF 3 CO 2 - and CF 3 SO 3 - ) with pyrazinecarbonitrile (MPCI = methyl pyrazine-2-carboximidate). Both compounds are composed of methyl pyrazine-2-carboximidate (MPCI), in which the pyrazinecarbonitrile ligand is transformed into an MPCI by methanolysis in the presence of silver(I) ions. The coordination geometry around silver(I) ion in 1 is a distorted tetrahedral structure, while two silver(I) ions in the asymmetric unit of 2 are a seesaw-like structure and a square-planar one. Furthermore, 1 and 2 display one-dimensional ladder-like coordination polymers due to the π–π interactions. 1 shows a visible light emission ranging from violet to blue wavelengths, whereas 2 appears a weak visible emission at around 470 nm.

Co-crystallization of a versatile building block 4-amino- 3,5-bis(4-pyridyl)-1,2,4-triazole with R-isophthalic acids (R = –H, –NH2, –SO3H, and –COOH): polymorphism and substituent effect on structural diversity

Co-crystallization of a versatile building module 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole (4-bpt) with isophthalic acid (H2ip) and its 5-substituted derivatives R–H2ip (R = –NH2, –SO3H, and –CO2H) affords a series of supramolecular solids 1–5. All compounds have been characterized by IR, microanalysis, and powder X-ray diffraction, and their thermal stability has been investigated by TG-DTA technique. Single crystal X-ray diffraction reveals that compounds 1 and 2 with the formula [(H2ip)·(4-bpt)] exhibit polymorphism, which can be isolated via a similar synthetic procedure without or with the metal ion as structure-directing reagent, and display distinct hydrogen-bonding assemblies of 3-D and double-layer networks, respectively. Multifarious 3-D supramolecular architectures are observed for compounds [(NH2–H2ip)·(4-bpt)] (3), [(SO3–H2ip)−·(H-4-bpt)+]·2H2O (4), and [(CO2H–H2ip)·(4-bpt)]·2H2O (5), in which the substituent groups of isophthalic acid are involved in different hydrogen-bonding interactions. The results clearly display the substituent effect on the structural assembly of organic co-crystals, which will be significant in the rational design and construction of such crystalline materials with specific hydrogen-bonding networks.

Static and time-resolved photocrystallographic studies in supramolecular solids

Abstract The supramolecular solid state is a medium par excellence for photochemical studies of molecules in a well-defined environment. If the photoactive molecule is embedded within a strong photochemically-inert framework, reactions can proceed without breakdown of the crystal lattice. A number of examples of trans-cis and cis-trans reactions are presented. A variable temperature study of Zn-coordinated tiglic acid shows that the reaction is energy-controlled with a small activation energy of approx. 2 kJ/mol, dependent on the size of the cavity in which the molecule is located. Time-resolved studies of the instantaneous dimer-formation of an organic and an inorganic species are presented. The Cu(I)(NH3)2 cation forms a dimeric species with a contracted Cu(I)—Cu(I) distance through promotion of an electron from an antibonding to a weakly bonding orbital, whereas xanthone forms an excimer with decrease interplanar spacing. The concept of the photodifference map is defined and used thoughout the article.

Mechanochemical Preparation of Molecular and Supramolecular Organometallic Materials and Coordination Networks

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Supramolecular solids and time-resolved diffraction

Supramolecular solids are an ideal medium for time-resolved diffraction studies at atomic resolution as they allow dilution of the active species, and the study of a species in different states of aggregation and different environments, but attention must be paid to excited-state quenching due to energy transfer. Crystallinity must be preserved up to reasonable product concentrations if chemical reactions are to be monitored at the atomic level.

Mechanochemical preparation of molecular and supramolecular organometallic materials and coordination networks

This Dalton Perspective deals with solvent-free reactions taking place within solids or between solids or involving a solid and a vapour. The focus is on reactions involving organometallic and coordination compounds and occurring via reassembling of non-covalent bonding, e.g. hydrogen bonds, and/or formation of ligand-metal coordination bonds. It is argued that reactions activated by mechanical mixing of solid reactants as well as those obtained by exposing a crystalline solid to a vapour can be exploited to "make crystals", which is the quintessence of crystal engineering. It is demonstrated through a number of examples that solvent-free methods, such as co-grinding, kneading, milling of molecular solids, or reactions of solid with vapours represent viable alternative, when not unique, routes for the preparation of novel molecular and supramolecular solids as well as for the preparation of polymorphic or solvate modifications of a same species. The structural characterization of the products requires the preparation of single crystals suitable for X-ray diffraction, a goal often achieved by seeding.

Luminescence Quenching and Energy Transfer in Supramolecular Solids

This article summarizes recent progress on the light emission of guest molecules embedded in supramolecular crystals. It covers spectroscopic studies, as well as crystallographic and computational investigations, and focuses on the factors responsible for luminescence quenching in host−guest solids. Examination of energy levels calculated by time-dependent density functional theory and of the experimental host-absorption and guest-emission spectra supports the crucial role of energy level separations in intermolecular energy transfer and the resulting luminescence quenching, thus providing guidelines for the synthesis of long-lifetime luminescent materials.

Emission quenching of photoactive molecules embedded in supramolecular solids: Synthesis, structure and photoluminescence studies of benzil in a CMCR-based inclusion complex with a saturated linker molecule

Using a fully saturated linker, DPP [DPP = 1,3-di-(4-piperidyl)propane], a new CMCR-based (CMCR = C-methylcalix[4]resorcinarene) supramolecular complex incorporating benzil, CMCR-DPP-benzil-EtOH-H2O, and a corresponding benzil-free analogue CMCR-DPP-3EtOH, have been synthesized. Comparison of the TDDFT energy levels and the experimental host-absorption and guest-emission spectra, confirms that the emission quenching of benzil in a series of CMCR-linker frameworks can be attributed to the energy transfer from the guest to the host framework in the supramolecular solid and suggests strategies for increasing the lifetime of luminescent materials.