Crystal structures of the clathrate inclusion compounds formed by the host bis(isothiocyanato) tetrakis (4-methylpyridine) iron (II) with benzene,m-xylene andp-xylene as guests

Single crystal X-ray structures of three 1 : 1 (guest: host) compounds in which the Fe(NCS)₂ (4-methylpyridine)₄ complex is the host component and benzene,m-xylene andp-xylene are the respective guest components, are reported. The crystals of the inclusion compounds are tetragonalI4₁/a, with:a = 17.08(1),c = 23.66(3) Å (benzene clathrate);a = 17.17(1),c = 24.02(2) Å (m-xylene clathrate) anda = 17.12(1),c = 23.93(3) Å (p-xylene clathrate);Z = 8. The host complex molecule has the octahedral type of coordination of the N₆ donor system. The isothiocyanate ligands are intrans positions and related by twofold axial symmetry. The symmetry axis runs diagonally between the neighbouring, equatorial 4-methylpyridine (MePy) ligands. The two symmetrically independent McPy ligands form angles ofca. 45 and 55° with the equatorial Fe-N₄ plane. The absorption sites for guest molecules lie on centres of symmetry. Non-centrosymmetricm-xylene molecules occupy these sites randomly distributed over two orientations related by symmetry. The structures belong to the class oforganic zeolites since the cavities occupied by the guest molecules are interconnected to form a three-dimensional network.     

On the clathrate structures of syndiotactic poly(m-methylstyrene)

The crystal structures of clathrate forms of syndiotactic poly(m-methylstyrene) containing guest molecules having different steric hindrance (CS₂, benzene and orto-dichlorobenzene) are presented. The structures are all characterized by polymer chains in s (2/1)2 helical conformation and guest molecules packed in an orthorhombic unit cell according to the space group Pcaa. All the presented clathrates belongs to β class indipendently from the dimensions of the guest molecule. In this aspect they differ both from clathrate forms of syndiotactic polystyrene, all belonging to α class, and from clathrate forms of syndiotactic poly(p-methylstyrene) that belong to α or β class according to the steric hindrance of the guest molecule.     

Inclusion compounds formed between α,ω-(long-carbon-chain)-diaminecademium(II) tetracyanonickelate(II) host and aromatic guest molecules

Inclusion compounds with the general formula Cd(NH₂(CH₂) _n NH₂)Ni(CN)₄·xG were prepared forn=4 to 8, and for G of such an aromatic guest molecule as pyrrole, benzene, aniline, toluene, toluidine, xylene, xylidine, dichlorobenzene, trimethylbenzene, tetramethylbenzene, ethylbenzene, styrene, or isopropylbenzene, with varyingx. Generally, longer chain lengths of ,-diamine in the host permit the inclusion of bulkier guest molecules. However, the presence of an amino group on the phenyl ring of the guest appears to impart a special affinity with the hosts.     

[NH3CH2CHCH3NH3]][B8O11(OH)4]·H2O: Synthesis and characterization of the first 1D borate templated by 1,2-diaminopropane

A new hydrated borate compound, [NH₃CH₂CHCH₃NH₃]][B₈O₁₁(OH)₄]·H₂O 1, has been synthesized in the presence of 1,2-diaminopropane acting as a structure-directing agent under mild conditions. Its structure was determined by single crystal X-ray diffraction and further characterized FTIR, elemental analysis, powder X-ray diffraction and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic system, space group P2₁/c (No. 14), a=10.0787(7) Å, b=8.8482(6) Å, c=19.3097(4) Å, β=91.352(6)°, V=1721.53(2) Å³, and Z=4. The structure consists of infinite open-branched borate chains constructed from [B₃O₆(OH)] units, onto which the [B₅O₇(OH)₃] groups are grafted. It represents the first example of one-dimensional borate templated by an organic amine. The adjacent borate chains are further linked together by extensive hydrogen bonds to form a 3D supramolecular network. The diprotonated organic amines and guest water molecules are filled in the free space of the hydrogen-bonded network and interact with the inorganic framework by extensive hydrogen bonds.     

Solid-state and inclusion properties of hydrogen-bonded 1,3-cyclohexanedione cyclamers

During crystallization 1,3-cyclohexanedione self assembles into either hydrogen-bonded chains or hexameric rings depending on the solvent conditions. The hexameric rings, called cyclamers, are the subject of this paper. These unusual structures occlude benzene as a guest molecule. The structural and crystal chemical properties of these host-guest compounds are explored here with the use of crystal growth studies, X-ray powder patterns, and thermal analysis. The crystal structure of the benzene cyclamer of 5-methyl-1,3-cyclohexanedione is reported (hexagonal,a =b = 19.19(2)Å,c = 10.545(9)Å,R3,Z = 18,V = 3362(6)ų; 717 unique reflections,R = 0.062). An analysis of the stereochemical implications of cyclic directionality in these cyclamers is also discussed.Alfred P. Sloan Foundation Fellow, 1989–1991.     

二维多孔铜-间苯二腈配位聚合物用于阴离子交换及客体分子可逆吸附性的研究

The 2D porous copper（Ⅰ） complex with 1,3-dicyanobenzene （DCB）, [Cu（DCB）2]（PF6）（Me2CO） 1, exhibits channels along axis c, in which one molecule acetone and one anion PF6 per formula unit are included respectively. The reversible incorporation of guest acetone and acetonitrile, as well as the anion exchange from PF6^- to BF4^- or CF3SO3^-, was investigated by thermogravimetric （TG） analysis, ^1H NMR spectra and/or infrared absorption spectroscopy. Additionally, the incorporation of benzene and toluene into complex 1 was also discussed. Complex 1 exhibited size selectivity for guest inclusion or anion exchange.     

Crystal structures of ethylenediaminecadmium(II) tetracyanocadmate(II)-benzene(1/2) and ethylenediaminecadmium(II) tetracyanocadmate(II)

The crystal structure of ethylenediaminecadmium(II) tetracyanocadmate(II)-benzene(1/2),I, has been redetermined based on 1632 reflections collected anew for the crystal coated with epoxy resin, with a final conventionalR=0.038;I crystallizes in space groupP4₂22, witha=b=8.265(1) andc=15.512(3) Å, andZ=2. Ethylenediaminecadmium(II) tetracyanocadmate(II),II, is concluded to be identical with the residual metal complex host ofI, remaining after the liberation of the guest benzene molecules;II crystallizes from an aqueous solution containing bis- or tris-ethylenediaminecadmium(II) tetracyanocadmate(II) in space groupI4₁/acd, witha=b=14.366(1) andc=23.771(4) Å, andZ=16; refinement led to a conventionalR=0.043 for 1181 reflections. The bridging ethylenediamine ligand inI turns to a chelating one inII; dissociation and recombination should occur in the coordination sphere of the six-coordinate cadmium atom, whenII is derived fromI by the liberation of the guest molecules. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82018 (30 pages).Dedicated to Professor H. M. Powell.     

Syntheses,Characterizations, and Crystal Structures of Two New Organically Templated Borates

Two new organically templated borates, [H₂DAB][B₇O₉(OH)₅]·2H₂O ( 1 ) and [H₂DAB][B₇O₁₀(OH)₃] ( 2 ), have been synthesized under mild conditions in the presence of DAB acting as structure‐directing agent (DAB = 1,4‐diaminobutane). The structures were determined by single crystal X‐ray diffraction and further characterized by FTIR, elemental analysis, and thermogravimetric analysis. Both 1 and 2 crystallize in the same triclinic system, space group (No. 2); 1: a = 8.238(4) Å, b = 8.348 (5) Å, c = 14.574(8) Å, a = 101.050(3)°, β = 92.313(7)°, γ = 112.694(5)°, V = 900.3(8) ų, Z = 2; 2: a = 8.8769(3) Å, b = 9.3204(2) Å, c = 10.2204(5) Å, α = 74.474(2)°, β = 85.292(5)°, γ = 72.730(2)°, V = 778.01(5) ų, Z = 2. The structure of 1 consists of [B₇O₉(OH)₅]^2? groups, which represents the first example of organically templated heptaborate. The structure exhibits interesting hydrogen‐bonded network formed by borate polyanion [B₁₄O₂₀(OH)₆]^4?, which can be regarded as being constructed from the dehydration of the FBBs in 1 . The diprotonated organic amines are filled in the free space of the hydrogen‐bonded network and interact with the inorganic framework by extensive hydrogen bonds.     

Synthesis,crystallographic, and thermal properties of a new porous silica

A new porous tectosilicate has been synthesized in the presence of boric acid and 1, 2, 2, 6, 6-pentamethylpiperidine as guest molecules. It crystallizes in the monoclinic system with a_o=9.91 (1) Å, b_o=20.62 (3) Å, c_o=9.80 (2) Å, and -99.7 (2)⁰. After heat treatment at 820°C for 1 hour the guest molecules are set free whereas the silica host framework is retained. From crystal morphology and thermal behaviour it is concluded that the new material possesses channel-like voids.     

Enhanced and Heteromolecular Guest Encapsulation in Nonporous Crystals of a Perfluorinated Triketonato Dinuclear Copper Complex

The flexible host framework of a perfluorinated mononuclear copper complex, [Cu(L¹)₂] ( 1 , HL¹=3-hydroxy-1,3-bis(pentafluorophenyl)-2-propen-1-one), with a CuO₄ core reversibly encapsulated several organic guest molecules through electrostatic interactions in its crystals. Hence, the corresponding dinuclear complex, [Cu₂(L²)₂] ( 2 , H₂L²=1,5-dihydroxy-1,5-bis(pentafluorophenyl)-1,4-pentadien-3-one), was prepared to enhance guest recognition and the ability to separate molecular mixtures. Complex 2 comprises a Cu₂O₆ core and four pentafluorophenyl groups. In crystal 2 , cavities are formed on the axial sites of the metal core that are surrounded by pentafluorophenyl groups. The crystal of 2 encapsulates various guest molecules, that is, benzene ( 3 ), toluene ( 4 ), xylene ( 5 ), mesitylene ( 6 ), durene ( 7 ), and anisole ( 8 ). X-ray crystallographic and thermogravimetric (TG) studies show that three guest molecules are present in the crystal cavities. The number of guest molecules found in complex 2 was higher than that in complex 1 , for example, ( 2 )₃ ⋅ ( 6 )₁₀> 1⋅ ( 6 )₂, ( 2 )₂ ⋅ ( 7 )₇> 1⋅7 , or 2⋅ ( 8 )₃> 1⋅ ( 8 )₂. Naphthalene ( 9 ), was encapsulated in 2 to give 2⋅ ( 9 )₃, but not in 1 . In the crystal of complex 2 , heteromolecular guest encapsulation was confirmed, designated as 2⋅ ( 3 )₂ ⋅9 . TG analysis indicates that the thermal stability of the guest-included crystals of 2 is higher than that of 1 .     

Solvent‐Free One‐Step Photochemical Hydroxylation of Benzene Derivatives by the Singlet Excited State of 2,3‐Dichloro‐5,6‐dicyano‐p‐benzoquinone Acting as a Super Oxidant

Photoinduced hydroxylation of neat deaerated benzene to phenol occurred under visible‐light irradiation of 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ), which acts as a super photooxidant in the presence of water. Photocatalytic solvent‐free hydroxylation of benzene derivatives with electron‐withdrawing substituents such as benzonitrile, nitrobenzene, and trifluoromethylbenzene used as neat solvents has been achieved for the first time by using DDQ as a super photooxidant to yield the corresponding phenol derivatives and 2,3‐dichloro‐5,6‐dicyanohydroquinone (DDQH₂) in the presence of water under deaerated conditions. In the presence of dioxygen and tert‐butyl nitrite, the photocatalytic hydroxylation of neat benzene occurred with DDQ as a photocatalyst to produce phenol. The photocatalytic reactions are initiated by oxidation of benzene derivatives with the singlet and triplet excited states of DDQ to form the corresponding radical cations, which associate with benzene derivatives to produce the dimer radical cations, which were detected by the femto‐ and nanosecond laser flash photolysis measurements to clarify the photocatalytic reaction mechanisms. Radical cations of benzene derivatives react with water to yield the OH‐adduct radicals. On the other hand, DDQ ^{. ?} produced by the photoinduced electron transfer from benzene derivatives reacts with the OH‐adduct radicals to yield the corresponding phenol derivatives and DDQH₂. DDQ is recovered by the reaction of DDQH₂ with tert‐butyl nitrite when DDQ acts as a photocatalyst for the hydroxylation of benzene derivatives by dioxygen.     

Nesting inclusion compounds. The X-ray structure of the 15-crown-5 sodium diphenylethyl diphenylmethyl cyanoacetonate complex

The action of sodium cyanide ongem -diphenyl-chloropropanone under phase transfer conditions in the presence of 15-crown-5 yields the title compound as a minor product. The crystal structure of this complex reveals that, in the solid state, the [15-crown-5-Na⁺] guest species is found within a loose cage of diphenylethyl diphenyl cyanoacetonate molecules with one open side of the cage blocked by an adjacent 15-crown-5 molecule. Colourless crystals of the compound belong to the monoclinic space groupP21/n witha = 12,255(2) Å,b = 13,005(1) Å,c = 23,433(2) Å, = 95,92(1) ° andD _c = 1.23 g cm^–3 forZ = 4.     

Studies on clathrasils VIII. Nonasils-[4158], 88SiO2 · 8M8 · 8M9 · 4M20: Synthesis,thermal properties,and crystal structure

Nonasils-[4¹5⁸], 88SiO₂·8M⁸·8M⁹·4M²⁰, have been synthesized with 2-methylpyrrolidine, hexamethyleneimine, 2-(aminomethyl)-tetrahydrofuran, 1,2-diaminocyclohexane, 2-methylpiperidine, 2-methylpiperazine, 1-aminobutane, 2-aminobutane, and 2-aminopentane as guest molecules, M²⁰. The samples have been prepared from aqueous silicate solutions which were sealed in silica tubes and heated at about 200°C for several weeks. These clathrasils crystallize in space groupFmmm. For the nonasil with 2-aminopentane as the guest molecule and the unit cell dimensionsa _o=22.232(6) Å,b ₀=15.058(4) Å, andc _o=13.627(4) Å, the structure has been refined using 550 non-equivalent single crystal reflexions to a reliability factorR _w =0.125. The 3-dimensional 4-connected silica host framework has three types of cage-like voids, [5⁴6⁴], [4¹5⁸], and [5⁸6¹²], the latter housing the structure-controlling guest molecules, M²⁰. The non-spherical shape of the guest molecules is the most important factor for the formation of nonasils-[4¹5⁸]. On heating nonasils-[4¹5⁸] up to 950°C the organic guest species are driven out and the pure silica form of nonasil is obtained.Part of this study was presented at the 24th Jahrestagung der AGKr, Cologne, 1985 [1]. For part VII see [4].     

Amphiphilic Inclusion Spaces for Various Guests and Regulation of Fluorescence Intensity of 1,8‐Bis(4‐aminophenyl)anthracene Crystals

A host framework for inclusion of various guest molecules was investigated by preparation of inclusion crystals of 1,8‐bis(4‐aminophenyl)anthracene (1,8‐BAPA) with organic solvents. X‐ray crystallographic analysis revealed construction of the same inclusion space incorporating 1,8‐BAPA and eight guest molecules including both non‐polar (benzene) and polar guests (N,N‐dimethylformamide, DMF). Fluorescence efficiencies varied depending on guest molecule polarity; DMF inclusion crystals exhibited the highest fluorescence intensity (Φ_F=0.40), four times as high as that of a benzene inclusion crystal (Φ_F=0.10). According to systematic investigations of inclusion phenomena, strong host–guest interactions and filling of the inclusion space led to a high fluorescence intensity. Temperature‐dependent fluorescence spectral measurements revealed these factors effectively immobilised the host framework. Although hydrogen bonding commonly decreases fluorescence intensity, the present study demonstrated that such strong interactions provide excellent conditions for fluorescence enhancement. Thus, this remarkable behaviour has potential application toward sensing of highly polar molecules, such as biogenic compounds.     

Solvent extraction of calcium and strontium into nitrobenzene by using a synergistic mixture of hydrogen dicarbollylcobaltate and N,N,N′,N′-tetraisobutyl-2,6-dipicolinamide

Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of N,N,N′,N′-tetraisobutyl-2,6-dipicolinamide [T(iBu)DPA, L] has been investigated. The equilibrium data have been explained assuming that the species HL⁺, HL₂ ⁺, CaL₂ ²⁺, SrL₂ ²⁺ and SrL₃ ²⁺ are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene saturated with water have been determined.     

In‐situ cryocrystallization of 1,2‐dimethyl‐3‐nitrobenzene and 2,4‐dimethyl‐1‐nitrobenzene

The crystal structures of 1,2‐dimethyl‐3‐nitrobenzene, C₈H₉NO₂, and 2,4‐dimethyl‐1‐nitrobenzene, C₈H₉NO₂, which are liquids at room temperature, have been obtained through in‐situ cryocrystallization. Weak C—H...O and also π–π interactions are present in both crystal structures.     

Dynamic Molecular Tweezers Composed of Dibenzocyclooctatetraene Units: Synthesis,Properties, and Thermochromism in Host–Guest Complexes

Novel dynamic molecular tweezers (DMTs) 3 a , 3 b , 4 a , 4 b , and 5 b , composed of two tub‐shaped dibenzocyclooctatetraene (DBCOT) units, were designed and synthesized. The cyclooctatetraene (COT) rings of these DMTs readily invert in solution, and the molecular structure shows rigid syn and anti forms in an equilibrium mixture in solution. The syn and anti conformers can be observed by NMR. The isomerization barriers of 3 a , 3 b , 4 a , 4 b , and 5 b are in the range of 16.5–21.3 kcal mol^?1, depending on steric repulsion between substituents of the COT rings and protons of the central benzene ring. These DMTs form complexes with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) and 1,2,4,5‐tetracyano‐benzene (TCNB) in solution and in the solid state. The binding abilities of these DMTs increase with electron‐donating substituents on COT, which increase the electron densities of the cavity of the syn form, as supported by theoretical calculations. In addition, elongation of the terminal alkoxy chains of the DMTs was found to cause the enhancement of van der Waals contact with guest molecules. Therefore, 5 b , which has CH₂OMe groups on the COT rings and longer ethoxy groups on the terminal benzene rings, showed the highest electron density of the cavity and hence the highest binding ability with the electron‐deficient guest molecules. Interestingly, solutions of 3 b , 4 b , and 5 b show thermochromism in the presence of DDQ. A solution of 3 b or 4 b with DDQ in CHCl₃ is green due to charge‐transfer interaction at room temperature and the color changes from green to yellow upon heating to 60 °C and from green to blue upon cooling to ?40 °C, whereas the high complexation ability of 5 b with DDQ only shows a change in the shade of blue.     

Synergistic extraction of europium and americium into nitrobenzene by using hydrogen dicarbollylcobaltate and 1,2-(diphenylphosphino)ethane dioxide

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of 1,2-(diphenylphosphino)ethane dioxide (DPPEtDO, L) has been investigated. The equilibrium data have been explained assuming that the species HL⁺, HL₂ ⁺, ML₂ ³⁺ and ML₄ ³⁺ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability constants of the corresponding complexes EuL _n ³⁺ and AmL _n ³⁺, where n = 2, 4 and L is DPPEtDO, in water-saturated nitrobenzene are comparable.     

Nanoporosity,Inclusion Chemistry,and Spin Crossover in Orthogonally Interlocked Two‐Dimensional Metal–Organic Frameworks

[Fe(tvp)₂(NCS)₂] ( 1 ) (tvp=trans‐(4,4′‐vinylenedipyridine)) consists of two independent perpendicular stacks of mutually interpenetrated two‐dimensional grids. This uncommon supramolecular conformation defines square‐sectional nanochannels (diagonal≈2.2 nm) in which inclusion molecules are located. The guest‐loaded framework 1@guest displays complete thermal spin‐crossover (SCO) behavior with the characteristic temperature T_1/2 dependent on the guest molecule, whereas the guest‐free species 1 is paramagnetic whatever the temperature. For the benzene–guest derivatives, the characteristic SCO temperature T_1/2 decreases as the Hammet σ_p parameter increases. In general, the 1@guest series shows large entropy variations associated with the SCO and conformational changes of the interpenetrated grids that leads to a crystallographic‐phase transition when the guest is benzonitrile or acetonitrile/H₂O.     

Crossover Sorption of C2H2/CO2 and C2H6/C2H4 in Soft Porous Coordination Networks

Porous sorbents are materials that are used for various applications, including storage and separation. Typically, the uptake of a single gas by a sorbent decreases with temperature, but the relative affinity for two similar gases does not change. However, in this study, we report a rare example of “crossover sorption,” in which the uptake capacity and apparent affinity for two similar gases reverse at different temperatures. We synthesized two soft porous coordination polymers (PCPs), [Zn₂(L1)(L2)₂]_n (PCP-1) and [Zn₂(L1)(L3)₂]_n (PCP-2) (L1= 1,4-bis(4-pyridyl)benzene, L2=5-methyl-1,3-di(4-carboxyphenyl)benzene, and L3=5-methoxy-1,3-di(4-carboxyphenyl)benzene). These PCPs exhibits structural changes upon gas sorption and show the crossover sorption for both C₂H₂/CO₂ and C₂H₆/C₂H₄, in which the apparent affinity reverse with temperature. We used in situ gas-loading single-crystal X-ray diffraction (SCXRD) analysis to reveal the guest inclusion structures of PCP-1 for C₂H₂, CO₂, C₂H₆, and C₂H₄ gases at various temperatures. Interestingly, we observed three-step single-crystal to single-crystal (sc-sc) transformations with the different loading phases under these gases, providing insight into guest binding positions, nature of host–guest or guest-guest interactions, and their phase transformations upon exposure to these gases. Combining with theoretical investigation, we have fully elucidated the crossover sorption in the flexible coordination networks, which involves a reversal of apparent affinity and uptake of similar gases at different temperatures. We discovered that this behaviour can be explained by the delicate balance between guest binding and host–guest and guest-guest interactions.