Donor−Acceptor Interaction and Photochemistry of Polymethylene-Linked Bichromophores in Solution
摘要:
The ground-state and the excited-state spectroscopic properties of four series of polymethylene-linked anthracene-dialkylaniline bichromophores were compared as a probe to the relationship between energetics and distance in photoinduced electron transfer (PET). The results demonstrate that, when the energy level of the charge transfer (CT) stale is lowered below that of the localized excited state by appropriate substituents, there is a strong electron-donor-acceptor (EDA) interaction in the ground state which is absent in other bichromophores. Absorption and fluorescence excitation studies revealed that there is an unusually strong EDA interaction in the ground state of A-2 which is absent in other members in the A series. When A-2 is excited directly into this EDA absorption, it exhibits two CT emissions, one at 490 nm and the other at 605 nm. The quantum yield (tau(f)) and the lifetime (Phi(f)) of the two emissions are dependent on the viscosity of the alkane solvent. The Phi(f) and the tau(f) of the 490 nm emission increased when the solvent viscosity tvas increased; however, those of the 605 nm emission remained essentially unchanged. The risetime of the 605 nm emission is 420 ps, but that of the 490 nm emission is instrument-function limiting. The results suggest that the two CT emissions may be derived from the two different conformations of the CT state. The 490 nm emission may be derived from the trans conformer of A-2, which is the major conformer at equilibrium. The EDA interaction in the trans conformer of A-2 may be treated as a type of through-sigma-bond interaction via the spacer between the n orbital of the anilino nitrogen and the pi orbital of the anthryl group. The direct excitation of A-2 from its EDA ground state to the CT state indicates that PET may occur in a sigma-linked bichromophoric system upon light absorption, thus reaching the limiting rate of a photochemical process.
Systematic Investigation of Photoinduced Electron Transfer Controlled by Internal Charge Transfer and Its Consequences for Selective PdCl<sub>2</sub>Coordination
作者:Thomas Schwarze、Wulfhard Mickler、Carsten Dosche、Roman Flehr、Tillmann Klamroth、Hans-Gerd Löhmannsröben、Peter Saalfrank、Hans-Jürgen Holdt
DOI:10.1002/chem.200902281
日期:2010.2.8
fluorophore–spacer–receptor format were prepared for detection of PdCl2 by fluorescence enhancement. The fluorescent probes 1–13 consist of a fluorophore group, an alkyl spacer and a dithiomaleonitrile PdCl2 receptor. First, varying the length of the alkylene spacer (compounds 1–3) revealed a dominant through‐space pathway for oxidative photoinducedelectrontransfer (PET) in CH2‐bridged dithiomaleonitrile fluoroionophores
Viscosity improver grafted with unsaturated acylating agent and a polyaromatic hydrocarbon
申请人:McDougall Patrick J.
公开号:US09234153B2
公开(公告)日:2016-01-12
Disclosed is an oil-soluble lubricating oil additive composition, suitable for use as a dispersant viscosity index improver in lubricating oils; prepared by the process which comprises reacting a hydrocarbon polymer having a number average molecular weight (Mn) between about 7,000 and about 500,000 wherein the polymer backbone has been functionalized with an ethylenically unsaturated acylating agent and a hydroxyl-linked polycyclic fused ring component.