The Preparation of Acryloxyl Group Functionalized Siloxane Polymers and the Study of Their Ultra Violet Curing Properties.

Polysiloxane with multiple acryloxyl groups at the terminal site of the polymer chain was synthesized by the condensation reaction between hydroxyl-terminated polysiloxane and acryloyl chloride and used to improve the cross-linking density of UV-curable silicone materials initiated from dual acryloxy-terminated symmetric polysiloxane or single acryloxy-terminated asymmetric polysiloxane with the mixture of Irgacure 1173 and Irgacure 184 at a mass ratio of 1:1 as the photoinitiator. The effects of factors such as initiator composition, UV irradiation time, structure, and molecular weight of linear dual acryloxy-terminated or single acryloxy-terminated asymmetric siloxane oligomers on the gelation yield, thermal properties, water absorption, and water contact angle of UV-cured film were investigated. The synthesized cross-linking density modifier can be copolymerized with acryloxy-functionalized linear polysiloxanes under the action of a photoinitiator to increase the cross-link density of UV-cured products effectively. Both linear dual acryloxy-terminated or single acryloxy-terminated asymmetric siloxane oligomers can be copolymerized with cross-link density modifiers within 20 s of UV irradiation. The gelation yields of the UV-cured products obtained from the dual acryloxy-terminated siloxane oligomers were greater than 85%, and their surface water contact angles increased from 72.8° to 95.9° as the molecular weight of the oligomers increased. The gelation yields of UV-cured products obtained from single acryloxy-terminated asymmetric siloxane oligomers were less than 80%, and their thermal stabilities were inferior to those obtained from the dual acryloxy-terminated siloxane oligomers. However, the water contact angles of UV-cured products obtained from these single acryloxy-terminated asymmetric siloxane oligomers were all greater than 90°.

Preparation of Monotrimethoxylsilylethyl-Terminated Polysiloxane Fluids and Their Application in Thermal Interface Materials.

In this study, α-Trimethylsilylmethyl-ω-dimethylsilyl-terminated polydimethylsiloxane, polydiethylsiloxane and poly[2,2,2-trifluoropropyl(methyl)siloxane] are synthesized using an anion catalyzed nonequilibrium polymerization reaction with trimethylsilylmethyl lithium as the initiator; hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane or 1,3,5-trimethyl-1,3,5-trifluoropropylcyclotrisiloxane as the monomer; and dimethylchlorosilane as an end-capping agent. Three kinds of α-trimethylsilylmethyl-ω-trimethoxylsilylethyl-terminated polysiloxanes are further prepared by hydrosilylation reaction of α-trimethylsilylmethyl-ω-dimethylsilyl-terminated polysiloxanes with vinyltrimethoxysilane using Karstedt's catalyst. These α-trimethylsilylmethyl-ω-trimethoxylsilylethyl-terminated polysiloxanes are functionalized as in situ surface treatment agents for AlN particles. The effects of the structure of these polysiloxanes on the dispersion of AlN in the polysiloxane matrix and on the heat transfer performance of silicone pastes and silicone rubbers are investigated. A possible mechanism of surface treatment of AlN fillers by these novel silicone fluids is also discussed.

Si-Bridged annulated BODIPYs: synthesis, unique structure and photophysical properties.

Two novel Si-bridged meso-annulated BODIPY dyes have been prepared through intermolecular C-I silylation and subsequent intramolecular C-H silylation in a one-pot reaction. A marked redshift of the main spectral bands was observed since the efficient σ*-π* conjugation results in a notable stabilization of the LUMOs. Si-annulation blocks the non-radiative decay and contributes to higher fluorescence quantum yields. This strategy is very attractive for the construction of highly emissive polycyclic aromatic hydrocarbons.

Oligosilanyl-Bridged Biscarbazoles: Structure, Synthesis, and Spectroscopic Properties.

Oligosilanyl-bridged systems are expected to give rise to unique optoelectronic properties because of σ-π conjugation between the Si-Si σ orbital and the aryl π orbital. Herein, we synthesized a small series of novel biscarbazoles bridged with permethylated oligosilanyl units (-[Si(CH3)2]n-, n = 1-4) and examined their spectroscopic properties in detail. In the target molecules BCzSin , n = 2-4, the efficient σ-π conjugation elevated the highest occupied molecular orbital energy level with no influence on the lowest unoccupied molecular orbital. In the solid state, the emission full width at half-maximum (fwhm) of all the compounds narrowed significantly, while the emission efficiency increased and the emission color of carbazole was retained. This research provided a very simple and general way of subtly manipulating the electronic properties of organic materials to construct an emissive color-retaining system for multifunctional applications.

Thieno[3,2-b]thiophene fused BODIPYs: synthesis, near-infrared luminescence and photosensitive properties.

The fusion of π-sufficient heteroaryl moieties has proven to be an effective strategy for achieving the red shift of the main spectral bands of BODIPY. In this paper, thieno[3,2-b]thiophene-fused BODIPY derivatives 1 and 2 have been designed and characterized by various spectroscopic methods, and their photosensitive properties have also been explored. Both dyes absorb in the near-infrared region with extremely high molar extinction coefficients, due to the extension of π-conjugation by fusion of the thieno[3,2-b]thiophene moiety. Their fluorescence quantum yields and singlet oxygen generation properties are significantly affected by iodine substitutions; dye 2 displays a moderate singlet oxygen generation value of 0.32, which makes it a potential NIR photosensitizer for photodynamic therapy of cancer in future research.

Two competing ionization processes in ESI-MS analysis of N-(1,3-diphenylallyl)benzenamines: formation of the unusual [M-H]+ ion versus the regular [M+H]+ ion.

A series of N-(1,3-diphenylallyl)benzenamine derivatives (M) were investigated by electrospray ionization mass spectrometry in the positive-ion mode. Both the anomalous [M-H]+ and the regular [M+H]+ were observed in the ESI mass spectra. The occurrence of [M-H]+ has been supported by accurate mass spectrometry, liquid chromatography mass spectrometry, and tandem mass spectrometry analysis. Calculation results indicated that formation of [M-H]+ is attributed to the ion-molecule reaction of M with the protonated ESI solvent molecule (e.g. CH3OH2+) via hydride abstraction from a tertiary Csp3-H. The competing ionization processes leading to [M-H]+ or [M+H]+ were significantly affected by the concentration of formic acid in the electrospray ionization solvent and the proton affinity of the N atom.

Crystal structure of bis-[2-(1H-benzimid-azol-2-yl)-4-bromo-phenolato-κ(2) N (3),O]cobalt(II).

The asymmetric unit of the title Co(II) complex, [Co(C13H8BrN2O)2], contains two independent mol-ecules (A and B). In both mol-ecules, the Co(II) cation is N,O-chelated by two 2-(1H-benzimidazol-2-yl)-4-bromo-phenolate anions in a distorted tetra-hedral geometry. In mol-ecule A, both chelating rings display an envelope conformation, with the flap Co atom lying 0.614 (6) and 0.483 (6) Šfrom the mean planes of the remaining atoms. In mol-ecule B, both chelating rings are approximately planar, the maximum deviations being 0.039 (4) and 0.076 (3) Å. In the crystal, mol-ecules are linked by classical N-H⋯O hydrogen bonds and weak C-H⋯O and C-H⋯Br hydrogen bonds into a three-dimensional supra-molecular network. Extensive π-π stacking is observed between nearly parallel aromatic rings of adjacent mol-ecules with centroid-centroid distances in the range 3.407 (3)-3.850 (4) Å.

1-(4-Bromo-benz-yl)-2-(4-bromo-phen-yl)-1H-benzimidazole.

There are two mol-ecules in the asymmetric unit of the title compound, C20H14Br2N2. In the first, the dihedral angles between the mean plane of the benzimidazole group and those of the 4-bromo-benzyl and 4-chloro-phenyl groups are 50.72 (17) and 71.29 (16)°, respectively, while the corresponding angles in the second mol-ecule are 42.09 (16) and 89.05 (17)°. The 4-bromo-benzyl and 4-bromo-phenyl groups make an angle of 68.1 (2) and 85.1 (21)° with each other in the two mol-ecules. In the crystal, weak C-H⋯N and C-H⋯Br hydrogen bonds link the mol-ecules along the c-axis direction. Br⋯Br inter-actions [3.5733 (9)Å] are also observed.

Expanding the coordination cage: a ruthenium(II)-polypyridine complex exhibiting high quantum yields under ambient conditions.

A mononuclear ruthenium(II) polypyridyl complex with an enlarged terpyridyl coordination cage was synthesized by the formal introduction of a carbon bridge between the coordinating pyridine rings. Structurally, the ruthenium(II) complex shows an almost perfect octahedral N6 coordination around the central Ru(II) metal ion. The investigation of the photophysical properties reveals a triplet metal-to-ligand charge transfer emission with an unprecedented quantum yield of 13% and a lifetime of 1.36 mus at room temperature and in the presence of air oxygen. An exceptional small energy gap between light absorption and light emission, or Stokes shift, was detected. Additionally, time-dependent density functional theory calculations were carried out in order to characterize the ground state and both the singlet and triplet excited states. The exceptional properties of the new compound open the perspective of exploiting terpyridyl-like ruthenium complexes in photochemical devices under ambient conditions.

5-p-Tolyl-1H-tetra-zole.

The title compound, C(8)H(8)N(4), possesses crystallographic mirror symmetry, with four C atoms lying on the reflecting plane, which bis-ects the phenyl and tetra-zole rings. It is composed of a planar r.m.s. deviation (0.0012 Å) tetra-zole ring which is nearly coplanar with the benzene ring, the dihedral angle being 2.67 (9)°. In the crystal, symmetry-related mol-ecules are linked by inter-molecular N-H⋯N hydrogen bonds. The mol-ecules stack along [100] with a π⋯π inter-action involving the phenyl and tetra-zole rings of adjacent mol-ecules [centroid-centroid distance = 3.5639 (15) Å]. The H atom of the N-H group is disordered over two sites of equal occupancy. The methyl H atoms were modelled as disordered over two sets of sites of equal occupancy rotated by 60° with respect to each other.

2-Carb-oxy-1-phenyl-ethanaminium nitrate.

In the title salt, C(9)H(12)NO(2) (+)·NO(3) (-), the cation and anion are linked by a bifurcated N-H⋯(O,O) hydrogen bond. The crystal packing is stabilized by inter-molecular N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds, which connect neighbouring cations and anions, resulting in a two-dimensional network.

2-Carb-oxy-1-(3-nitro-phen-yl)ethanaminium perchlorate.

In the cation of the title compound, C(9)H(11)N(2)O(4) (+)·ClO(4) (-), the conformation is stabilized by an intra-molecular N-H⋯O hydrogen bond. In the crystal packing, centrosymmetrically related cations inter-act through inter-molecular O-H⋯O hydrogen bonds involving the carb-oxy groups, forming dimers. The dimers and the perchlorate anions are further linked into layers parallel to the ab plane by C-H⋯O and N-H⋯O hydrogen-bonding inter-actions.

Dimethyl 1-cyano-methyl-1H-pyrazole-3,5-dicarboxyl-ate.

The title mol-ecule, C(9)H(9)N(3)O(4), syhthesized from 1H-pyrazole-3,5-dicarboxylic acid and 2-bromo-acetonitrile, is approximately planar; the inter-planar angles between the pyrazole ring and the mean planes of the two carboxylate units and the cyanomethyl unit are 4.49 (10), 5.56 (9) and 5.03 (19)°, respectively. In the crystal, inversion dimers linked by pairs of weak C-H ⋯O bonds occur, and the packing is further stabilized by aromatic π-π stacking [centroid-centroid separation = 3.793 (4) Å].

2-Carb-oxy-1-phenyl-ethanaminium perchlorate.

In the title compound, C(9)H(12)NO(2) (+)·ClO(4) (-), an intra-molecular N-H⋯O inter-action results in the formation of a six-membered ring having a twisted chair conformation. In the crystal structure, inter-molecular O-H⋯O, N-H⋯O and C-H⋯O inter-actions link the mol-ecules into a network. A weak C-H⋯π inter-action is also found.

3-(2-Pyrid-yl)-5-(4-pyrid-yl)-4-(p-tol-yl)-1H-1,2,4-triazole.

In the mol-ecule of the title compound, C(19)H(15)N(5), the dihedral angles formed by the plane of the triazole ring with those of the 2-pyridyl, 4-pyridyl and p-tolyl rings are 28.12 (10), 34.62 (10) and 71.43 (9)°, respectively. The crystal structure is consolidated by C-H⋯π hydrogen-bonding inter-actions and by π-π stacking inter-actions, with a centroid-centroid distance of 3.794 (4) Å.

Oxonium 2-carb-oxy-3-(2-fur-yl)acrylate.

In the title compound, H(3)O(+)·C(8)H(5)O(5) (-), neighbouring cations and anions are linked by O-H⋯O hydrogen bonds, forming a one-dimensional chain framework along [001]. The crystal structure is further stabilized by π-π inter-actions, with centroid-centroid distances of 3.734 (3) Å.

Redetermination of 3-(ammonio-meth-yl)pyridinium dichloride.

The crystal structure of the title compound, C(6)H(10)N(2) (2+)·2Cl(-), has been reported previously in the non-standard setting P2(1)/a [Genet (1965 ▶). Bull. Soc. Fr. Miner. Crist.88, 463-470], with an R value of 0.16. The current redetermination improves significantly the precision of the geometric parameters. In the crystal packing, cations and anions are linked by inter-molecular N-H⋯Cl and C-H⋯Cl hydrogen bonds into a three-dimensional network.

2-(Chloro-meth-yl)benzimidazolium chloride.

The structure of title compound, C(8)H(8)ClN(2) (+)·Cl(-), comprises discrete ions which are inter-connected by N-H⋯Cl hydrogen bonds, leading to a neutral one-dimensional network in [001]. This hydrogen bonding appears to complement π-π stacking inter-actions [centroid-centroid distances 3.768 (2) and 3.551 (2) Å] and helps to stabilize the structure further.

Does the surface matter? Hydrogen-bonded chain formation of an oxalic amide derivative in a two- and three-dimensional environment.

We report on a multi-technique investigation of the supramolecular organisation of N,N-diphenyl oxalic amide under differently dimensioned environments, namely three-dimensional (3D) in the bulk crystal, and in two dimensions on the Ag(111) surface as well as on the reconstructed Au(111) surface. With the help of X-ray structure analysis and scanning tunneling microscopy (STM) we find that the molecules organize in hydrogen-bonded chains with the bonding motif qualitatively changed by the surface confinement. In two dimensions, the chains exhibit enantiomorphic order even though they consist of a racemic mixture of chiral entities. By a combination of the STM data with near-edge X-ray absorption fine-structure spectroscopy, we show that the conformation of the molecule adapts such that the local registry of the functional group with the substrate is optimized while avoiding steric hindrance of the phenyl groups. In the low coverage case, the length of the chains is limited by the Au(111) reconstruction lines restricting the molecules into fcc stacked areas. A kinetic Monte Carlo simulated annealing is used to explain the selective assembly in the fcc stacked regions.