Clathrate Complex Research Articles

Thermal and pressure-induced spin crossover in a novel three-dimensional Hoffman-like clathrate complex

The synthesis and crystal structure of the interpenetrated metal–organic framework material Fe(bpac)2[Ag(CN)2]2 (bpac = 4,4′-bis(pyridyl)acetylene) are reported along with the characterization of its spin crossover properties by variable temperature magnetometry and Mossbauer spectroscopy. The complex presents an incomplete stepped spin transition as a function of temperature that is modified upon successive thermal cycling. The pressure-induced transition has also been investigated by means of high pressure Raman spectroscopy using a diamond anvil cell. The results show that it is possible to reach the thermally-inaccessible fully low spin state at room temperature by applying hydrostatic pressure to the sample.

Complexation of Syndiotactic Polystyrene with 12‐Crown‐4

Solid-state complexation of syndiotactic polystyrene (sPS) with a crown ether compound, 1,4,7,10-tetraoxa-cyclododecane (12-crown-4), took place when a film of sPS/chloroform clathrate was subjected to a guest exchange procedure assisted with a plasticizing agent. The new guest 12-crown-4 molecules were incorporated into the crystalline region of the sPS film, without causing a large conformational change of host sPS helices. X-ray diffraction and thermogravimetric investigations showed that sPS/12-crown-4 complex had a clathrate complex structure which contained four 12-crown-4 molecules per unit cell. IR and Raman data suggested that 12-crown-4 took a C(i) -type conformation in the sPS complex phase.

Radiation-Induced Inclusion Polymerization of β (−)Pinene In Deoxycholic Acid

For the first time, β (−)pinene has been successfully polymerized by the radiation-induced inclusion polymerization technique in deoxycholic acid (DOCA) crystals. The resulting poly-β (−)pinene (pBp) has been isolated in the pure form from the host matrix in very high yield (nearly 100% on the starting monomer at 320 kGy), while the pBp yield from bulk radiolysis of β (−)pinene is very low ≈ 3%. The clathrate complex pBp@DOCA and the pure pBp from inclusion polymerization have been studied by FT-IR spectroscopy, thermogravimetric analysis (TGA and DTG) and by differential thermal analysis (DTA). The optical activity of pBp from inclusion polymerization has been investigated by polarimetry and by optical rotatory dispersion (ORD) spectroscopy. Evidences have been found about the phenomenon of asymmetric induction “through space” caused by the chiral host matrix on the guest pBp molecules.

In Situ Spectroscopic, Electrochemical, and Theoretical Studies of the Photoinduced Host−Guest Electron Transfer that Precedes Unusual Host-Mediated Alkane Photooxidation

In the unusual photooxidation of alkanes within the cavity of a self-assembled M(6)L(4) cage complex (1), the proposed reaction mechanism involves the generation of the host anion radical and guest cation radical via guest-to-host photoinduced electron transfer (PET). In the present study, the postulated host anion radical was elucidated by in situ IR spectroscopy. The difference IR spectrum before and after the irradiation of the clathrate complex 1a [symbol: see text] (2)(4) (2 = adamantane) features a dominant negative peak at approximately 1500 cm(-1), which is attributed to the decrease in the CN stretching vibration and thus indicative of the structural change in the triazine core of the cage. Electrochemical measurements and theoretical calculations show the remarkably great electron-accepting ability of the triazine core. These results strongly support the proposal of guest-to-host PET.

Catena-Poly[[[trimethyltin(IV)]-μ-4,4′-bipyridyl-κ2N:N′-[trimethyltin(IV)]-μ-1,3,4-thiadiazole-2,5(3H)-dithionato(2−)-κ2N3:S5] 4,4′-bipyridine clathrate

In the title clathrate complex, {[Sn2(CH3)6(C2N2S3)(C10H8N2)]·C10H8N2}n, two independent Sn atoms are five-coordinated in a distorted trigonal–bipyramidal geometry. The asymmetric unit contains two independent 4,4′-bipyridine systems, one of which bridges two independent Sn atoms [Sn—N = 2.588 (7) and 2.591 (7) A], leading to the formation a one-dimensional polymeric zigzag chain.

Probing Guest Geometry and Dynamics through Host–Guest Interactions

The highly symmetric structure of a cagelike host enables the inclusion geometry of guest molecules in the host to be predicted in a dynamic fashion by analyzing not the guest but the host framework. For example, an S4 orientation of two 1,2-diketone guests in the clathrate complex was predicted by NMR spectroscopy and subsequently confirmed by X-ray analysis (see picture).

Probing Guest Geometry and Dynamics through Host-Guest Interactions

The highly symmetric structure of a cagelike host enables the inclusion geometry of guest molecules in the host to be predicted in a dynamic fashion by analyzing not the guest but the host framework. For example, an S4 orientation of two 1,2-diketone guests in the clathrate complex was predicted by NMR spectroscopy and subsequently confirmed by X-ray analysis (see picture).

Ab initio and lattice dynamics studies of the vibrational and geometrical properties of the molecular complex of hydroquinone and C 60

The 3:1 complex of β-hydroquinone (HQ β) and C 60 has been studied by ab initio and lattice dynamics calculations. The geometry of C 60 in a cage has been calculated within the Hartree–Fock scheme and the charge-transfer and guest–host interactions have been investigated. The equilibrium geometry of C 60 in the cage is similar to the geometry of the isolated C 60 and no charge transfer occurs, in agreement with previous experimental data. Our study of this C 60 clathrate complex revealed that the stability and dynamical behavior of the host structure are strongly dependent on the guest molecules and hence on guest–host interactions.

Three-dimensional structure of the clathrate complex [{Ni(NCS)2(H2O)2(dabco)2 }·dabco]·2dmso obtained from zero valent metal (dabco = 1,4-diazabicyclo[2.2.2]octane and dmso = dimethyl sulfoxide)

The new clathrate complex [{Ni(NCS) 2 (H 2 O) 2 (dabco) 2 }· dabco]·2dmso (dabco = 1,4-diazabicyclo[2.2.2]octane and dmso = dimethyl sulfoxide), the first example of a compound comprising metal centres and dabco molecules in a 1:3 ratio, has been prepared from metal powder; its crystal structure contains [Ni(NCS) 2 (H 2 O) 2 (dabco) 2 ] ∞ square grids linked by hydrogen-bonded dabco molecules to afford a three-dimensional framework, molecules of dmso occupy square-shaped channels.

Use of the Rapid Visco‐Analyzer to Measure Starch Pasting Properties part II: Effects of Emulsifiers and Sugar‐Emulsifier Interactions

AbstractThe Rapid Visco‐Analyzer (RVA) was used to study the effects of sucrose ester (SE) emulsifiers and a propylene glycol ester (PGE) emulsifier on starch cooking properties. Maize, tapioca and wheat starches were affected to different degrees by F‐160 SE with a hydrophil‐lipophil balance (HLB) of 15. Up to a concentration of 0.05 parts emulsifier to 1 part starch, the F‐160 SE increased peak viscosity, time to peak and maximum setback viscosity of the starches. These data suggested that the SE functioned by forming a clathrate complex with the starch molecules. When cooking properties of maize starch were studied in the presence of SEs with HLB 6, 11 and 15, the effects of the SE did not appear to be directly related to HLB. The PGE did not appear to form a clathrate complex with wheat starch, as indicated by a decrease in peak viscosity and time to peak. Cooking properties of the starches were also measured in the presence of sugars (dextrose, sucrose, corn syrup solids and polydextrose) at a level of 2 parts sugar to 1 part starch, plus emulsifiers at a ratio of 0.02:1. Peak viscosity, time to peak and maximum setback viscosity were affected synergistically in the presence of both sugar and emulsifier as compared to additive effects of the two ingredients acting alone. Although reaction mechanisms could not be defined from the data obtained, the RVA proved useful for quickly demonstrating the effects of multiple ingredients on starch cooking properties.

Electron Spin Resonance of Radical Pairs in X-Irradiated Single Crystals of Clathrate Complex of Hydroquinone with Acetonitrile

Electron Spin Resonance of Radical Pairs in X-Irradiated Single Crystals of Clathrate Complex of Hydroquinone with Acetonitrile