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Electronic Influence (electronic + influence)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Symmetric Versus Unsymmetric Platinum(II) Bis(aryleneethynylene)s with Distinct Electronic Structures for Optical Power Limiting/Optical Transparency Trade-off Optimization

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009
Guijiang Zhou
Abstract A new series of symmetric and unsymmetric Pt(II) bis(acetylide) complexes of the type DC,CPt(PBu3)2C,CD (DPtD), AC,CPt(PBu3)2C,CA (APtA) and DC,CPt(PBu3)2C,CA (DPtA) (D, donor groups; A, acceptor groups) are synthesized, and show superior optical power limiting (OPL)/optical transparency trade-offs. By tailoring the electronic properties of the aryleneethynylene group, distinct electronic structures for these metalated complexes can be obtained, which significantly affect their photophysical behavior and OPL properties for a nanosecond laser pulse at 532,nm. Electronic influence of the ligand type and the molecular symmetry of metal group on the optical transparency/nonlinearity optimization is thoroughly elucidated. Generally, aryleneethynylene ligands with , electron-accepting nature will effectively enhance the harvesting efficiency of the triplet excited states. The ligand variation to the OPL strength of these Pt(II) compounds follows the order: DPtD,>,DPtA,>,APtA. These results could be attributed to the distinctive excited state character induced by their different electronic structures, on the basis of the data from both photophysical studies and theoretical calculations. All of the complexes show very good optical transparencies in the visible-light region and exhibit excellent OPL responses with very impressive figure of merit ,ex/,o values (up to 17), which remarkably outweigh those of state-of-the-art reverse saturable absorption dyes such as C60 and metallophthalocyanines with very poor transparencies. Their lower optical-limiting thresholds (0.05,J,cm,2 at 92% linear transmittance) compared with that of the best materials (ca. 0.07,J,cm,2 for InPc and PbPc dyes) currently in use will render these highly transparent materials promising candidates for practical OPL devices for the protection of human eyes and other delicate electro-optic sensors. [source]

Optical Power Limiters Based on Colorless Di-, Oligo-, and Polymetallaynes: Highly Transparent Materials for Eye Protection Devices,

ADVANCED FUNCTIONAL MATERIALS, Issue 6 2007
G.-J. Zhou
Abstract The synthesis, characterization, and photophysics of a series of solution-processable and tractable di-, oligo-, and polymetallaynes of some group 10,12 transition metals are presented. Most of these materials are colorless with very good optical transparencies in the visible spectral region and exhibit excellent optical power limiting (OPL) for nanosecond laser pulse. Their OPL responses outweigh those of the state-of-the-art reverse saturable absorption dyes such as C60, metalloporphyrins, and metallophthalocyanines that are all associated with very poor optical transparencies. On the basis of the results from photophysical studies and theoretical calculations, both the absorption of triplet and intramolecular charge-transfer states can contribute to the enhancement of the OPL properties for these materials. Electronic influence of the type, spatial arrangement, and geometry of metal groups on the optical transparency/nonlinearity optimization is evaluated and discussed in detail. The positive contribution of transition metal ions to the OPL of these compounds generally follows the order: Pt,>,Au,>,Hg,>,Pd. The optical-limiting thresholds for these polymetallaynes can be as low as 0.07,J,cm,2 at 92,% linear transmittance and these highly transparent materials manifest very impressive figure of merit ,ex/,o values (up to 22.48), which are remarkably higher than those of the benchmark C60 and metal phthalocyanine complexes. The present work demonstrates an attractive approach to developing materials offering superior OPL/optical transparency trade-offs and these metallopolyynes are thus very promising candidates for use in practical OPL devices for the protection of human eyes and other delicate optical sensors. [source]

Synthesis, Characterization, and Protonation Reactions of Ar-BIAN and Ar-BICAT Diimine Platinum Diphenyl Complexes

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2010
Jerome Parmene
Abstract PtII diphenyl complexes (N,N)PtPh2 [N,N = diimines Ar,N=C(An)C=N,Ar with Ar = substituted aryl groups] have been prepared and characterized by 1H, 13C, and 195Pt NMR spectroscopy. The 195Pt NMR spectroscopic data establish the electronic influence exerted by substituents at the backbone of the diimine ligand system to the metal center. When compared to diimines Ar,N=CMe,CMe=N,Ar, the electron-withdrawing ability of the Ar-BIAN ligand and the electron-donating ability of the O,O-heterocyclic Ar-BICAT systems are demonstrated. Trends in 195Pt NMR chemical shifts suggest that electronic tuning of the metal center is better achieved through variations of the diimine backbone substituents rather than variation of the substituents at the N-Aryl groups. Protonation of (N,N)PtPh2 in dichloromethane/acetonitrile at ,78 °C furnishes the corresponding PtIV hydrides (N,N)PtPh2H(NCMe)+. The PtIV hydrides liberate benzene with the formation of (N,N)PtPh(NCMe)+ when the temperature is raised. A second protonation and rapid benzene elimination produces the dicationic PtII species (N,N)Pt(NCMe)22+ at approximately 50 °C. Protonation of (N,N)PtPh2 in the absence of acetonitrile results in the clean formation of (N,N)PtPh(,2 -C6H6)+ at temperatures that depend on the steric hindrance provided by the alkyl substituents at the diimine N-aryl groups. These findings support the notion that the metal is the kinetically preferred site of protonation. The results qualitatively agree with a recent mechanistic study of protonation-induced reactions of (diimine)PtPh2 complexes that bear simple methyl substituents at the diimine backbone. Several compounds have been crystallographically characterized. All complexes have the expected square planar environment at the metal. Modest variations in the metric parameters suggest that the Ar-BICAT system has a weaker trans influence than the Ar-BIAN and Ar-DAB systems. [source]

Superelectrophilic Activation of N -Substituted Isatins: Implications for Polymer Synthesis, a Theoretical Study

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 2 2009
Daniel Romero Nieto
Abstract The stability and reactivity of mono- and multi-protonatred N -substituted isatin derivatives were studied at PBE0/aug-cc-pvtz//PBE0/6-31+G** level of theory in triflic acid (TFSA) solution. Calculations showed that the monocationic intermediates are the principal reactive species in the reaction of hydroxyalkylation of isatin derivatives in TFSA media. Electron-withdrawing substituents on the nitrogen atom increase the reactivity of isatin-containing electrophiles towards aromatic hydrocarbons, in accordance with their expected electronic influence. Steric factors also play an important role in the reactivity of isatin-containing electrophiles, especially in the second reaction step, due to their more sterically hindered reactive center. [source]