Inclusion of methylviologen dication in a cadmium tetracyanoplatinate host clathrate showing photochromism and photoluminescence modulation

A cadmium tetracyanoplatinate host clathrate, (MV)[Cd₂{Pt(CN)₄}₃]?2(H₂O) (1), including a methylviologen dication (MV²⁺) was synthesized, and the crystal structures, photochromic and photoluminescence properties were investigated. In 1, the alternatively parallel stacking between the MV²⁺ dications as electron acceptors in the channels and the electron donors [Pt1(CN)₄]^2– units in the host frameworks give a unique donor-acceptor (DA) system. Under UV irradiation, the electron transfer between MV²⁺ and [Pt(CN)₄]^2– ions generates MV^·+ radicals with a photochromic behavior from pale-yellow to blue. This process occurs through single-crystal-to-single-crystal (SCSC) transformation and obvious structure variation of viologen cations is successfully observed. Moreover, the spectral overlap between the emission bands of 1 and the absorption around 623 nm for the MV^·+ radicals leads to a modulation of the photoluminescence.     

Crystal structures of syndiotactic poly(p-methylstyrene) clathrates with two guest molecules having very similar shape and volume

In the present paper we report on the clathrate structures of syndiotactic poly(p-methylstyrene) (s-PPMS) containing chlorobenzene (cell constants: a = 23.5 Å, b = 12.0 Å, c = 7.9 Å and γ = 112.4°; space group: P2₁/a) and toluene (cell constants: a = 19.5 Å, b = 13.5 Å, c = 7.9 Å and γ = 90°; space group: P2₁). Despite the extreme similarity between the shape and volume of these two molecules, they give rise to completely different clathrate structures, the first belonging to α class, the second belonging to β class. Moreover the clathrate form containing chlorobenzene represent the first case in which a α class clathrate form of s-PPMS contains two guest molecules in each cavity while the crystal structure here proposed for the s-PPMS/toluene clathrate represents a new example of chiral crystalline phase in which the polymer helices assume all the same chirality in the lattice. These results underline the fact that the choice of a particular structural organization in the process of clathrates’ formation of s-PPMS is not easily referable only to steric effects but seems to be dependant even on the chemical structure of the guest molecules. A comparison with syndiotactic polystyrene is also done.     

Synthesis and spectroscopic properties of the elusive 3a,9a-diazaperylenium dication

The 3a,9a-diazaperylenium dication (1) was synthesized for the first time in two steps from p-phenylene diamine. Ab initio calculations show a twisted ground state with a 6.4 degrees tilt between the two quinolizinium building blocks. Dication 1 is photoluminescent in fluid solutions of H(2)O, CH(3)CN, and CH(3)NO(2), but not in rigid matrices of the same solvents. This phenomenon has been attributed to a geometric relaxation of the tilted ground state into an emitting planar lowest singlet excited state. [structure: see text]     

A charge-transfer complex of 10,10'-dihydroxy-9,9'-biphenanthryl and methylviologen as a visual inclusion host system

A charge-transfer (CT) complex, composed of 10,10'-dihydroxy-9,9'-biphenanthryl as the electron donor and 1,1'-dimethyl-4,4'-bipyridinium dichloride as the electron acceptor, is formed only by the inclusion of guest molecules. The color of this inclusion CT complex is sensitive to the component guest molecules.     

Crystal structures of two syn bent tetraalkylhydrazines,their radical cations,and a dication

The crystal structures of 2,7-diazatetracyclo[6.2.2.2^3,6.0^2.7]tetradec-4-ene, 2, its cation radical nitrate salt 2⁺, NO₃^-, 2,7-diazatetracyclo[6.2.2.2^3,6.0^3,7]tetradecane, 3, its dication dihexafluorophosphate salt 3²⁺(PF₆^-)₂, and a low quality structure of the monocation radical tosylate salt of 3 are reported and compared with MNDO calculations of these structures. Cations 2⁺ and 3⁺ are found to be significantly syn bent at nitrogen, and the dication 3²⁺ has a longer N-N distance than its azo analogue, 2,3-diazabicyclo [2.2.2]oct-2-ene (11).     

The synthesis and properties of a methylviologen analogue

A novel derivative of methylviologen, prepared by transannular reaction of [2.2] (3,5) pyridinophane, shows large bathochromic shift in the electronic spectrum and nearly equal redox potential compared with methylviologen.     

Crystal structures and luminescence properties of two new terbium complexes with aromatic carboxylic acid

Two new terbium complexes with aromatic carboxylic acids, [(Tb)₂(L₁)₆(H₂O)₄] (1) and [(Tb)₂(L₂)₆(H₂O)₂(DMF)₂] (2) (HL₁: nicotinic acid; HL₂: 4-hydroxybenzoic acid), with different coordination geometries have been synthesized and their crystal structures determined. The luminescence properties of the two complexes, including the phosphorescence lifetime, have been investigated. The effect of a secondary ligand on luminescence of the ternary terbium complex with carboxylic acid and the relationship between luminescence properties and crystal structure, including coordination mode of the carboxyl groups from HL₁ and HL₂ and coordination mode of a secondary ligand, are discussed.     

Red electrophosphorescence from a soluble binaphthol derivative as host and iridium complex as guest

The investigation of the optical properties, carrier injection, and transport into a soluble small molecule, 6,6'-dicarbazolyl-2,2'-dihexyloxy-1,1'-binaphthol (BA), was reported. The results demonstrated that BA is a blue-emitting molecule, which can be used as a host for the fabrication of electrophosphorescent light-emitting diodes (LEDs). The single-layer electrophosphorescent LEDs fabricated from toluene solution containing BA with tris[2,5-bis-2'-(9',9'-dihexylfluorene)pyridine-kappa(2)NC(3)(')]iridium(III) [Ir(HFP)(3)] emitted red light from Ir(HFP)(3) triplet emission. The results from photoluminescence (PL) and electroluminescence (EL) demonstrated that the dominated operational mechanism in EL was charge trapping rather than F?rster transfer, which was the dominated mechanism in PL. The single-layer OLEDs with 1wt % of Ir(HFP)(3) have a luminance (L) of 1000 cd/m(2) at 22 V and a luminous efficiency (LE) of 0.88 cd/A at 11 mA/cm(2). Double-layer electrophosphorescent LEDs fabricated by casting the emitting layer from a solution of BA blended with Ir(HFP)(3) and subsequently thermally depositing tris(8-hydroxyquinoline) aluminum (Alq(3)) film as an electron injection and transport layer yielded L = 1830 cd/m(2) at 30 V and LE = 2.47 cd/A at 18 mA/cm(2). These results demonstrated that electrophosphorescent LEDs can be fabricated from BA via solution processing and that L and LE can be enhanced by changing the device architecture with the goal of better balancing the electron and hole currents.     

二茂铁基亮氨酸锌配合物的晶体结构与性质

二茂铁基手性氨基酸类化合物由于兼有二茂铁衍生物和手性氨基酸的特点,如稳定性高、氧化还原性、毒性低、能够提供较好的手性环境等优点,在不对称催化、识别等方面的研究逐渐引起了人们的关注.     

Two clathrates of bis(isothiocyanato)tetrakis(4-methylpyridine)magnesium(II) as a host with 4-methylpyridine as a guest

Two clathrate modifications of the title host with 4-methylpyridine (4-CH₃C₅H₄N) as a guest have been determined at –50°C. [Mg(4-CH₃C₅H₄N)₄(NCS)₂] · 2/3(4-CH₃C₅H₄N) · 1/3H₂O is trigonal, space group , witha=27.630(7),c=11.219(3) ÅV=7417(4) ų,Z=9,D _calc=1.171 g cm^–3,(CuK )=18.506 cm^–1, finalR=0.064. [Mg(4-CH₃C₅H₄N)₄(NCS)₂] · (4-CH₃C₅H₄N) is tetragonal, space group I4_l/a, witha=16.944(7),c=23.552(9)Å,V=6762(5) Å,Z=8,D _calc=1.191 g cm^–3, (CuK )=18.200 cm^–1, finalR=0.071.The structures consist of molecular packings of the same host complex units and the guest species. The Mg(II) cation is octahedrally coordinated to theN-atoms of four 4-methylpyridine and twotrans-coordinated isothiocyanato ligands in the host molecule. The conformations of the molecule are considerably different both in symmetry and in geometry in these two structures. The guest 4-methylpyridine molecules are disordered into channels which have different topology in these two clathrates resulting in different thermal stability.     

Crystal structures and spectroscopic properties of a new zinc phosphite cluster and an unexpected chainlike zinc phosphate obtained by hydrothermal reactions

A new zinc phosphite cluster, Zn₂(4,4′-dmbpy)₂(H₂PO₃)₄1, and a new chainlike zinc phosphate, Zn₂(5,5′-dmbpy)₂(HPO₄)(H₂PO₄)₂2, have been synthesized under hydrothermal conditions (4,4′-dmbpy=4,4′-dimethyl-2,2′-dipyridy, 5,5′-dmbpy=5,5′-dimethyl-2,2′-dipyridy). Compound 1 is a molecular zinc phosphite constructed from ZnO₃N₂ trigonal bipyramids, H₂PO₃ pseudo-pyramids and 4,4′-dmbpy ligands. Compound 2 possesses a 1D chainlike framework constructed from ZnO₃N₂ trigonal bipyramids, HPO₄ tetrahedra, H₂PO₄ tetrahedra and 5,5′-dmbpy ligands. Both compounds 1 and 2 exhibit intensive photoluminescence originated from the intraligand π-π* transitions. Crystal data: 1, monoclinic, P2₁/n, , , , β=110.857(3)°, , Z=2, R1=0.0297, wR₁=0.0801; 2, triclinic, P-1, , , , α=64.995(9)°, β=65.952(9)°, γ=65.296(8)°, , Z=2, R₁=0.0418, wR₁=0.1010.     

Europium complex of a tridentate ligand: synthesis and spectroscopic properties

A new europium complex containing the chelate tridentate ligand and imidazole terpyridine (itpy), was synthesized. The complex was characterized by elemental analysis, mass, FT-IR and photoluminescence spectroscopic techniques. The europium complex in solution showed characteristic luminescence properties. The room temperature photoluminescence spectrum of this complex was composed of typical Eu³⁺ red emission assigned to ⁵D₀ → ⁷F₂ transition. The metal-centered red emission seemed to be promoted by the ligand-assisted energy transfer, namely antenna effect.     

Synthesis and thermal and spectroscopic properties of macrocyclic vinyl aromatic polymers

Well‐defined and narrow molecular weight distribution macrocyclic poly(2‐vinylnaphthalene) (P2VN) and poly(2‐vinyl‐9,9‐dimethylfluorene) (PDMVF) containing a single 1,4‐benzylidene or 9,10‐anthracenylidene unit have been synthesized via the potassium naphthalide initiated polymerization of the monomers followed by the end‐to‐end coupling of the resulting P2VN dianions under high‐dilution conditions with 1,4‐bis(bromomethyl)benzene or 9,10‐bis(chloromethyl)anthracene. Molecular characterization has been carried out by size exclusion chromatography, nuclear magnetic resonance, differential scanning calorimetry, ultraviolet–visible spectroscopy, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. The thermal properties show distinct differences between the cyclic and matching linear polymers, with the macrocycles showing much higher glass‐transition and decomposition temperatures. The absorption bands are both hyperchromic and hypochromic with respect to the model aromatic compounds, and this is consistent with intensity borrowing. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5488–5503, 2004     

Zn(II) pyrazolonate complexes obtained by metal-induced cyclization of thiosemicarbazones: Crystal structures and spectroscopic properties

The reaction of zinc(II) acetate with thiosemicarbazones derived from β-keto esters (methyl propionylacetate thiosemicarbazone, ethyl benzoylacetate thiosemicarbazone, ethyl 2-ethylacetoacetate thiosemicarbazone and methyl acetoacetate ¹N-ethylthiosemicarbazone) induces the cyclization of the thiosemicarbazone to afford [ZnL₂] and (in one case) [ZnL₂(MeOH)] complexes, where HL is a substituted 2,5-dihydro-5-oxo-1H-pyrazolone-1-carbothioamide. The four complexes were studied by X-ray diffraction, which showed that the pyrazolonate ligand binds with the metal through the S and N(3) atoms. The influence of cyclization and metallation on the ¹H and ¹³C NMR spectra of the starting thiosemicarbazones is also discussed.     

Crystal structures,spectroscopic and nonlinear optical properties of metal complexes of Schiff-base ligands containing nitrogen and sulfur donors

ML2 type CuII chelates with the Schiff base ligands R-C6H4CHNNHC(S)SCH2Ph (R=NMe2 or -OMe) have been prepared and characterized. Spectroscopic data suggest that the Schiff bases act as singly charged anionic bidentate ligands, forming stable neutral metal complexes. Magnetic and e.s.r. data support a square-planar coordination geometry for both complexes. Single crystal X-ray diffraction analysis of the complexes has established that the Schiff base ligand is deprotonated to give the thiol tautomer, coordinated via the thiolato sulfur and β-nitrogen. The geometry around the metal is square-planar with two equivalent Cu-N and Cu-S bonds; the two phenyl rings and the donor atoms are in one plane forming an extensive electronic delocalization system. Third-order optical nonlinearity measurements show that the complexes exhibit fairly large second-order hyperpolarizabilities. This revised version was published online in June 2006 with corrections to the Cover Date.     

Crystal structure and spectroscopic properties of CsVO2SO4

Dark crystals of the V(V) compound CsVO(2)SO(4), suitable for X-ray investigations have been obtained from the catalytically important Cs(2)S(2)O(7)-V(2)O(5) system. By cooling of the mixture with the composition X(V)2(O)5 = 0.5, some crystals were obtained in the otherwise glassy sample. The compound crystallizes in the orthorhombic space group Pbca with a = 6.6688(13) A, b = 10.048(2) A, and c = 17.680(4) A at 20 degrees C and Z = 8. It contains a coordination sphere with a short V-O bond of 1.595(2) A and trans to this the closest VO distance at 3.4 A and four equatorial V-O bonds in the range 1.725(1)-1.984(2) A. The deformation of the VO(6) octahedron is thus much more pronounced compared to other known oxo sulfato V(V) compounds, and the coordination polyhedron of V(V) should be regarded as a tetragonal pyramid with the vanadium atom in the center. Each VO(2)(+) group is coordinated to the neighboring groups by oxygen and sulfate double bridges in a zigzag structure where two sulfate oxygens virtually remain uncoordinated-one is found at the very long nonbonding V-O distance from the neighboring chain. This is the first time that we find pentacoordination of vanadium in the 12 different V(III), V(IV), and V(V) compounds examined so far. The FTIR and Raman spectra of the compound are in agreement with the simple formula unit of the investigated compound.     

Crystal structures and certain properties of hapnium-beryllium compounds

Summary The system Hf-Be was investigated by x-ray structural and microstructural analysis and by determinations of microhardness. The existence of four compounds was established: {ie402-1}Translated from Zhurnal Strukturnol Khimil, Vol. 2, No. 4, pp. 424–433, July–August 1961     

Hydrophobic interactions in the formation of a complex between a polycationic water-soluble oxacalix[4]arene and a neutral aromatic guest

Abstract

Polycationic oxacalix[4]arene 1·4HCl was found to be able to recognise, in water, the neutral π-rich aromatic guest 2,7-dihydroxynaphthalene, despite earlier studies indicating that the binding cleft of the oxacalixarene is π rich in nature. ¹H NMR titrations at different pH values demonstrate that the tricationic receptor 1·3H⁺ displays the highest affinity towards DHN. According to a combination of NMR data and semiempirical (PM6) calculations, hydrophobic interactions play a prominent role in the formation of the complex.