Crystal Solvates Research Articles

Crystal solvates of zinc(II) bis(dipyrrinates) with triethylamine: composition, stability and spectral-luminescent properties

Crystal solvates of 2,2′-, 2,3′- and 3,3′-bis(dipyrrinato)zinc(II) with triethylamine (TEA) were obtained by slow crystallization. Composition, structural organization, stability, and spectral-luminescent properties of the crystal solvates were studied by FTIR, Powder X-ray Diffraction, thermal, mass spectral, absorption and fluorescence analyses. The thermal dissociation processes of crystal solvates in an argon atmosphere have been investigated. It is shown that zinc(II) helicates with decamethylsubstituted 2,2′-, 2,3′-, and 3,3′-bis(dipyrrin)s with TEA form stable supramolecular complexes of the composition [Zn2L2(TEA)4] and [Zn2L2TEA]. Spectroscopic studies showed that the quantum yield (φ) of [Zn2L2(TEA)n] crystal solvates in cyclohexane is noticeably (3–4.5 times) lower than φ of [Zn2L2] complexes. Quantum chemical study indicated the most likely mechanism for the coordination of solvent molecules on the coordinating centers of [Zn2L2]. Thermal and energy stability of [Zn2L2(TEA)n] solvates reduced when replacing the 2,2′- on 2,3′-, and 3,3′-isomer. The obtained results are of interest for the development of [Zn2L2] fluorescent sensors of the electron donor molecules.

Conformational properties and folding analysis of a series of seven oligoamide foldamers

33 crystal structures (11 unsolvated and 22 solvates) of a series of seven oligoamide foldamers were analysed. The crystal structures revealed that despite the structural and environmental differences the series of foldamers prefer only two general conformations, a protohelical @-conformation and a sigmoidal S-conformation. Both conformations also have preferred crystal packing motifs and solvate forming tendencies. Hydrogen bonding was found to be the most decisive factor in conformational preference, but steric properties, the type of the peripheral substituents, as well as solvent and aromatic interactions were also found to have an effect on the conformational details and crystal form.

Highly porous hydrogen-bond networks from a triptycene-based catechol

Solvate crystals of 9,10-dimethyl-2,3,6,7,14,15-hexa(hydroxy)-triptycene (1) form a variety of 3D hydrogen-bonded topologies, including bcu, acs, bsn and an apparently new 7-connected net. Several of these networks contain 1D or 2D arrays of solvent-filled channels, amounting to up to 60% solvent-accessible void space.

Different Spin-State Behaviors in Isostructural Solvates of a Molecular Iron(II) Complex.

The complex [FeL2][BF4]2 (1; L=4-(isopropylsulfanyl)-2,6-di(pyrazol-1-yl)pyridine) forms solvate crystals 1⋅solv (solv=MeNO2, MeCN, EtCN, or Me2 CO). Most of these materials lose their solvent sluggishly on heating. However, heating 1⋅MeNO2 at 450 K, or storing 1⋅EtCN under ambient conditions, leads to single-crystal to single-crystal exchange of the organic solvent for atmospheric moisture, forming 1⋅H2O. Solvent-free 1 (1⋅sf) can be generated in situ by annealing 1⋅H2O at 370 K in the diffractometer or magnetometer. The different forms of 1 are isostructural (P21 /c, Z=4) and most of them exhibit spin-crossover (SCO) at 141 ≤ T1/2 ≤ 212 K, depending on their solvent content. The exception is the EtCN solvate, whose pristine crystals remain high-spin between 3-300 K. The cooperativity of the spin-transitions depends on the solvent, ranging from gradual and incomplete when solv=acetone to abrupt with 17 K hysteresis when solv=MeCN. Our previously proposed relationship between molecular structure and SCO explains some of these observations, but there is no single structural feature that correlates with SCO in all the 1⋅solv materials. However, changes to the unit cell dimensions during SCO differ significantly between the solvates, and correlate with the SCO cooperativity. In particular, the percentage change in unit cell volume during SCO for the most cooperative material, 1⋅MeCN, is 10 times smaller than for the other 1⋅solv crystals.

Solid Forms, Crystal Habits, and Solubility of Danthron

The polymorphism, crystal habits, and solubility of 1,8-dihydroxyanthraquinone (danthron) were investigated in acetic acid, acetone, acetonitrile, n-butanol, and toluene. The solubility was determined for the commercially available form (FI) from 293.15 K to 318.15 K by the gravimetric method. The influence of solvents on crystal habit and polymorphic form has been investigated. Three different crystal habits of danthron were obtained from slow evaporation and cooling experiments. By evaporation, thin squares of FI were obtained from n-butanol and toluene solutions while both FI and fine needles of FII were obtained from acetone and acetonitrile solutions. In addition, needle-shaped solvate crystals were obtained from acetic acid solutions and the structure of the solvate was solved by single crystal X-ray diffraction. From cooling crystallization experiments, mixtures of FI and FII were often obtained from various solvents, but FI and FII possess distinct habits which can be easily distinguished by visua...

Piezoluminescence and Liquid Crystallinity of 4,4′-(9,10-Anthracenediyl)bispyridinium Salts

Piezoluminescence and liquid crystallinity of anthracene-based bispyridinium salts were investigated in stimulus-responsive luminescent organic crystals and luminescent ionic liquid crystals. The salts possess an anthracene moiety as a fluorophore in their center, and the pyridiniums attached to the anthracene moiety are substituted with trialkoxybenzyl groups. Single crystals of the salts bearing two trimethoxybenzyl groups were obtained as solvates. Ethyl acetate, acetone, and dioxane solvates of the chlorides have almost the same crystal structures with one-dimensional channels. Grinding of the solvated crystals caused the extrusion of the included solvent molecules, which resulted in the red shifts of their fluorescence in the solid state. The dimethyl sulfoxide solvate of the hexafluorophosphate also showed piezoluminescene by grinding. Tris(octyloxy)benzyl and tris(dodecyloxy)benzyl derivatives exhibited rectangular columnar liquid crystals upon being heated for their bromide and tetrafluoroborate s...

Crystal solvates of zinc(II) tetra-4-[(n-hexyloxy)benzoylamino]phthalocyanine

Desolvation processes of the crystal solvates of zinc(II) tetra-4-[(n-hexyloxy)benzoylamino]phthalocyanine formed with various organic solvents were studied. The physicochemical characteristics of destruction of the axial complexes of zinc(II) tetra-4-[(n-hexyloxy)benzoylamino]phthalocyanine with DMF, ethanol, and acetone were determined. In the case of chloroform, no axial complex is formed by this macrocycle.

Crystal Structure Analysis of Betti Base 1-((2-hydroxynaphthalen-1-yl)(2-hydroxyphenyl)methyl)urea•2DMF Solvate

A novel Betti base compound, 1-((2-hydroxynaphthalen-1-yl)(2-hydroxyphenyl)methyl)urea, UBB, was synthesized and characterized by spectral, structural and thermal studies. Single crystal X-ray diffraction studies reveal that the racemic mixture of the compound, when crystallized from DMF, yields R-isomer preferentially (prismatic crystals), whereas, when crystallized from 5:1 (v/v) mixture of DMF-THF, it yields S-isomer (rectangular shaped crystals) with two molecules of DMF, included in both the cases. The crystal structure is discussed in terms of supramolecular interactions and molecular modeling. Both R and S enantiomeric DMF solvate crystals are in their chiral triclinic P1 space group.

The crystal structure and morphology of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) p-xylene solvate: a joint experimental and simulation study.

The crystal structure of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaiso-wurtzitane (CL-20) p-xylene solvate, and the solvent effects on the crystal faces of CL-20 were studied through a combined experimental and theoretical method. The properties were analyzed by thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD).The growth morphology of CL-20p-xylene solvate crystal was predicted with a modified attachment energy model. The crystal structure of CL-20p-xylene solvate belonged to the Pbca space group with the unit cell parameters, a = 8.0704(12) Å, b=13.4095(20) Å, c = 33.0817(49) Å, and Z = 4, which indicated that the p-xylene solvent molecules could enter the crystal lattice of CL-20 and thus the CL-20 p-xylene solvate is formed. According to the solvent-effected attachment energy calculations, (002) and (11−1) faces should not be visible at all, while the percentage area of the (011) face could be increased from 7.81% in vacuum to 12.51% in p-xylene solution. The predicted results from the modified attachment energy model agreed very well with the observed morphology of crystals grown from p-xylene solution.

C60 -mediated molecular shape sorting: separation and purification of geometrical isomers.

A supramolecular crystallization-based approach has been developed for the shape-dependent separation of geometrical isomers under near-ambient conditions. Difficulties to separate such isomers arise because of their very similar physical properties. The present approach relies on the ability of C60 to preferentially form solvate crystals with molecules of a specific geometry. Subsequently, these molecules are released upon mild heating to regenerate pure C60 . By taking isomers of xylene and trimethylbenzene (TMB) as examples, we show that one of the isomers can be extracted from the rest with very high purity. To separate TMB isomers, a new C60 -1,3,5-TMB solvate was developed, which led to the isolation of isomer purities greater than 99.6 %. Versatility, a low operating temperature of approximately 100 °C, a separation efficiency of more than 10 weight % of C60 per cycle, and reagent recyclability makes this a promising molecular shape-sorting approach.

C60‐Mediated Molecular Shape Sorting: Separation and Purification of Geometrical Isomers

AbstractA supramolecular crystallization‐based approach has been developed for the shape‐dependent separation of geometrical isomers under near‐ambient conditions. Difficulties to separate such isomers arise because of their very similar physical properties. The present approach relies on the ability of C60 to preferentially form solvate crystals with molecules of a specific geometry. Subsequently, these molecules are released upon mild heating to regenerate pure C60. By taking isomers of xylene and trimethylbenzene (TMB) as examples, we show that one of the isomers can be extracted from the rest with very high purity. To separate TMB isomers, a new C60–1,3,5‐TMB solvate was developed, which led to the isolation of isomer purities greater than 99.6 %. Versatility, a low operating temperature of approximately 100 °C, a separation efficiency of more than 10 weight % of C60 per cycle, and reagent recyclability makes this a promising molecular shape‐sorting approach.

On the use of energetic compounds containing small molecules occluded in the structural cavities of the crystal

This paper presents an analysis of the possibility of improving the ballistic performance of solid rocket propellants by using the α-modification of hexanitrohexaazaisowurtzitane (CL-20) as a component of solid crystal hydrates or crystal solvates. If small molecules (water, hydrazine, and methanol) occluded in the main material are enclosed in the structural cavity of the crystal of the main component and, consequently, the crystal lattice parameters do not change relative to the original compound, then, there is a real opportunity to improve the ballistic performance of the rocket propellants developed on the basis of the original energetic compound by increasing the density of the component.

Thermostimulated structural changes in C60-CCl4 and C70-CCl4 crystal solvates

The crystal solvates in C60-CCl4 and C70-CCl4 systems obtained by crystallization from CCl4 solution at room temperature were studied by IR Fourier spectroscopy and X-ray diffraction. The C70 · (CCl4)n crystal solvate was obtained and studied for the first time; its hexagonal crystal lattice has unit cell parameters a = 10.658 ± 0.001 A and c = 10.811 ± 0.002 A. The temperature ranges of its destruction were determined.

Towards Controlling the Valance Tautomer Interconversion Character by Solvation

Valence tautomers are bi-stable functional molecular materials in which it is observed charge transference between redox active ligands and a metallic center followed by the change of spin of the metal. Valence tautomerism (VT) interconversion is entropically driven and induced by external stimuli such as irradiation by light and soft X-rays and/or changes in temperature and pressure. VT interconversion is also associated with remarkable variations in optical and magnetic properties and and can be modulated with slight chemical changes [1]. Typical examples of valence tautomers are coordination compounds of Co and o-dioxolenes ligands [2]. Crystals of the [Co(diox)(4-X-py)2], where diox = 3,5-di-t-butylcatecholate/3,5-di-t-butylsemiquinonate, X=CN/NO2, py= pyridine, were initially studied with respect to low spin (LS) to high spin (HS) thermo and photoinduced VT interconversion. It was reported that [Co(diox)(4-CN-py)2] crystals become HS–Co3+ at temperatures below 110 K with cooperative VT interconversion whereas [Co(diox)(4-NO2-py)2] crystals present non cooperative VT interconversion [3]. Toluene and benzene solvates of [Co(diox)(4-NO2-py)2 and [Co(diox)(4-CN-py)2 have been prepared to investigate further the solvation effects on the VT interconversion properties. Analysis of the single crystal X-ray diffraction data obtained during cooling and heating at temperatures ranging from 293 K to 90 K indicated that [Co(diox)(4-CN-py)2] toluene and benzene as well as [Co(diox)(4-NO2-py)2].toluene solvate crystals undergo into non cooperative VT interconversion. The [Co(diox)(4-NO2-py)2].benzene crystal show a highly cooperative VT interconversion with a pronounced hysteresis. Intermolecular interactions between inlayer [Co(diox)(4-X-py)2] molecules are responsible for the VT interconversion in all compounds, however the VT interconversion cooperativity seems to be related with the strength of the Car–H...Odiox interactions and with the correspondent Co–Co separation. Thus solvation plays a key role in the definition of the VT interconversion nature. Acknowledgments: FAPEMIG, CNPq and CAPES grant 10030-12-3.

Optical Properties of Three Crystal Modifications of a 2,3-Dicyanopyrazine Dye

Some pyrazine dyes are known to display strong fluorescence not only in solution but also in the solid-state. 5-t-Butyl-2,3-dicyano-6-[4-(dimethylamino)styryl]pyrazine (1) is a 2,3-dicyanopyrazine dye synthesized for an examination of substituent effects on thin-film growth [1]. Dye 1 was found to exhibit three crystal modifications with different color appearance (I: red, II: black, III: reddish purple). Modification I is a solvate crystal including one chloroform per one dye molecule [2], and modifications II and III are polymorphs. In this work, optical properties of these three modifications were interpreted on the basis of their crystal structures. The absorption spectra of the modifications were measured using optical waveguide spectroscopy. The absorption maxima of modifications I, II and III were found at 559 nm, 462 nm and 571 nm, respectively. A bathochromic absorption shift of reddish modifications I and III from that of 1 in toluene was 79 nm (-2944 cm-1) and 91 nm (-3320 cm-1), respectively. On the other hand, a hypsochromic absorption shift of 18 nm (812 cm-1) was observed in modification II. The fluorescence maxima of modifications I, II and III were found at 619 nm, 734 nm and 668 nm, respectively. The energy displacement corresponding to the observed spectral shifts was characterized in terms of an exciton interaction. The exciton interaction for a dimer was estimated using the extended dipole model, and the nearest-neighbor approximation was applied for evaluating a total energy displacement due to crystallization. The calculation results were qualitatively in good agreement with the observed spectral shifts. The result also revealed that molecular pairs in two-dimensional stacking structure in these modifications play a significant role in the total energy displacement.

Composition and thermal stability of bis (dipyrrolylmethenato)zinc(II) crystal solvates with N,N -dimethylformamide

Abstract Fluorescence of zinc(II) bis (dipyrrolylmethenates) [Zn 2 L 2 ] is very sensitive to the medium polarity. Fluorescence quantum yield ( φ ) of [Zn 2 L 2 ] reaches 0.99 in nonpolar media and close to zero in the electron donor solvents (amines, alcohols and other). Fluorescence quenching may be caused by the additional coordination of the electron donor molecules on the zinc atoms with formation of stable supramolecular structures [Zn 2 L 2 (Solv) n ]. For the confirming this assumption, the samples of the crystal solvates of 2,2′-, 2,3′- and 3,3′- bis (dipyrrolylmethenato)zinc(II) with N,N -dimethylformamide were obtained by slow crystallization. Spectroscopic studies showed that the quantum yield of crystal solvates in cyclohexane solutions is noticeably lower than φ for corresponding complexes [Zn 2 L 2 ]. The thermal dissociation processes of crystal solvates in an argon atmosphere have been investigated. It is shown that helicates of the zinc(II) with decamethylsubstituted 2,2′-, 2,3′- and 3,3′- bis (dipyrrolylmethenes) form with DMF stable supramolecular complexes of the composition [Zn 2 L 2 (DMF) 2 ]. Crystal solvates [Zn 2 L 2 (DMF) 2 ] are stable up to a temperature below ∼100 °C in an inert argon atmosphere and the values of the enthalpies of their thermal destruction process are 88–143 kJ/mol. The obtained results are of interest for the development on the basis of [Zn 2 L 2 ] of the fluorescent sensors of the electron donor molecules.

On Two Solvate Crystals of Di‐μ‐sulfido(‐dithiocarbamate)‐tin­(IV): [Sn(S2CNH2)2S]2·2H2O·EtOH and [Sn(S2CNH2)2S]2·­4EtOH

Abstract[Sn(S2CNH2)2S]2·2H2O·EtOH (A) was prepared via oxidation of Sn2+ with thiuram sulfide in aqueous alcohol solution. The compound [Sn(S2CNH2)2S]2·4EtOH (B) crystallizes from a saturated alcoholic solution of A. The monoclinic unit cell of A, space group P21/n (No. 14), a = 12.9169(9), b = 9.7222(5), c = 19.504(12) Å and β = 99.802(8) °, contains four formula units. B crystallizes in the orthorhombic space group Fddd (No. 70), a = 12.9500(4), b = 13.7737(4), c = 34.6012(12) Å with Z = 8 formula units per unit cell. The crystal structures consist of dinuclear Sn(S2CNH2)2 units doubly bridged by two sulfide (S2–) anions forming a centrosymmetric Sn2S2 square. These units are interlaced by primarily strong hydrogen bonds originating from the solvate molecules and the amino groups (O–H···S, N–H···O and N–H···S for A and N–H···O and O–H···S for B). The two solvate crystals can be interconverted via their alcoholic solution. B recrystallizes after saturation and A precipitates if a suitable portion of water is added.

Liquid crystalline phase behavior of silica nanorods in dimethyl sulfoxide and water.

We report lyotropic smectic liquid crystalline phase behavior of silica nanorods dispersed in binary mixtures of dimethyl sulfoxide (DMSO) and water (H2O). The phase behavior is affected by nanorod size polydispersity and DMSO concentration in the binary solvent. The isotropic to biphasic transition is strongly affected by the relative amount of DMSO in the solvent, but the solvent has little effect on the biphasic to liquid crystal transition above 40/60 DMSO/H2O by volume. At less than 40% DMSO, increasing silica nanorod concentration initially results in the formation of liquid crystalline domains, but further increasing silica concentration results in crystal solvate formation. The morphology of the liquid crystalline phase is strongly affected by the size polydispersity, with lower polydispersity leading to a more uniform structure. As in other lyotropic nanocylinder systems, the microstructure of continuous solid films produced from the dispersions was affected by both the initial microstructure and the applied shear.

Synthesis of potassium fluorophosphate hafnates at 20°C

Potassium fluorophosphate hafnates (PFPH) K3H3Hf3F3(PO4)5 and KHf2F3(PO4)2 · 2H2O were synthesized for the first time, and a KZr2F3(PO4)2 · 2H2O phase was found to exist. The compounds were studied by crystal-optical, elemental, X-ray powder diffraction, thermogravimetric, IR spectroscopic, and electron microscopic analyses. It was found that PFPH crystallize as one-dimensional nanoparticles. The IR spectra showed that PFPH K3H3M3F3(PO4)5 (M = Zr, Hf) are crystal solvate K3M3(PO4)5 · 3HF. Annealing of K3H3Hf3F3(PO4)5 and KHf2F3(PO4)2 · 2H2O at 1000°C gives rise to mixtures that mostly contain various phosphate hafnates.

Construction of covalent- and hydrogen-bonded assemblies from 1′,1′′′-biferrocenediboronic acid as a new organobimetallic building block

1',1'''-Biferrocenediboronic acid () was synthesized from 1',1'''-dibromobiferrocene by a typical procedure of converting Br to B(OH)2 groups in 76% yield and identified by (1)H-, (13)C- and (11)B-NMR and ESI-MS. X-ray diffraction (XRD) studies showed that, in non-solvated crystals (Form I), the new organobimetallic building block formed 1D hydrogen-bonded networks (i.e., chain) with octaatomic rings composed of the neighbouring two molecules. In solvated crystals with a composition of ()3(THF)2 (Form II), exists in two conformers (Conformers A and B) with respect to the rotation of the CpB(OH)2 moieties relative to the Cp rings of the fulvalenide moieties; Conformer A formed 1D hydrogen-bonded networks laterally hydrogen-bonding with THF molecules while Conformer B formed a new planar hydrogen-bonded motif involving four B(OH)2 groups and stepwise laminated networks of the planar motif. A macrocyclic tetraferrocenyl boronate ester was synthesized by cyclocondensation between and pentaerythritol in 33% yield and identified by (1)H-, (13)C- and (11)B-NMR, ESI-MS and XRD. In electrochemical measurements, the cyclocondensed compound exhibited four defined reversible waves with a total spread of 756 mV in CH2Cl2 containing n-Bu4NBArF4 (ArF = 3,5-bis(trifluoromethyl)phenyl), displaying both intra- and inter-biferrocenyl interactions.