scholarly journals Time-Resolved Spectroscopic and Density Functional Theory Investigation of the Photogeneration of a Bifunctional Quinone Methide in Neutral and Basic Aqueous Solutions

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3102 ◽  
Author(s):  
Zhiping Yan ◽  
Lili Du ◽  
Xin Lan ◽  
Yuanchun Li ◽  
Wenchao Wang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Density Functional Theory ◽  
Density Functional ◽  
Transient Absorption ◽  
Reaction Pathway ◽  
Resonance Raman Spectroscopy ◽  
Mixed Solution ◽  
Solution Ph ◽  
Functional Theory ◽  
Time Resolved

Binol quinone methides (BQMs) can be generated from 1,1′-(2,2′-dihydroxy-1,1′-binaphthyl-6,6′-diyl)bis(N,N,N-trimethylmethanamiuium) bromide (BQMP-b) in a 1:1 MeCN:H2O mixed solution via a ground state intramolecular proton transfer (GSIPT), as mentioned in our previously reported studies. Here, the photoreaction of BQMP-b in neutral and basic aqueous solution (pH = 7, 10, 12) was investigated to explore the possible mechanisms and the key intermediates produced in the process of the photoreaction and to examine whether they are different from those in a neutral mild-mixed MeCN:H2O solution. The studies were conducted using femtosecond transient absorption (fs-TA), nanosecond transient absorption (ns-TA), and nanosecond time-resolved resonance Raman spectroscopy (ns-TR3) in conjunction with results from density functional theory (DFT) computations. The results showed that BQMP-b was deprotonated initially and produced BQMs species more effectively through an E1bc elimination reaction in a strong basic aqueous condition (pH = 12), which differed from the reaction pathway that took place in the solution with pH = 7 or 10. A related single naphthol ring molecule 1-(6-hydroxynaphthalen-2-yl)-N,N,N-trimethylmethanaminium bromide (QMP-b) that did not contain a second naphthol ring was also investigated. The related reaction mechanisms are elucidated in this work, and it is briefly discussed how the mechanisms vary as a function of aqueous solution pH conditions.

scholarly journals Photochemical α-Cleavage Reaction of 3’,5’-Dimethoxybenzoin: A Combined Time-Resolved Spectroscopy and Computational Chemistry Study

Molecules ◽  
2020 ◽  
Vol 25 (15) ◽  
pp. 3548
Author(s):  
Yuanchun Li ◽  
Xiting Zhang ◽  
Zhiping Yan ◽  
Lili Du ◽  
Wenjian Tang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Quantum Yield ◽  
Dft Calculations ◽  
Density Functional ◽  
Transient Absorption ◽  
Type I ◽  
Functional Theory ◽  
Time Resolved ◽  
Norrish Type ◽  
Intramolecular Hydrogen

Benzoin is one of the most commonly used photoinitiators to induce free radical polymerization. Here, improved benzoin properties could be accomplished by the introduction of two methoxy substituents, leading to the formation of 3’,5’-dimethoxybenzoin (DMB) which has a higher photo-cleavage quantum yield (0.54) than benzoin (0.35). To elucidate the underlying reaction mechanisms of DMB and obtain direct information of the transient species involved, femtosecond transient absorption (fs-TA) and nanosecond transient absorption (ns-TA) spectroscopic experiments in conjunction with density functional theory/time-dependent density functional theory (DFT/TD-DFT) calculations were performed. It was found that the photo-induced α-cleavage (Norrish Type I reaction) of DMB occurred from the nπ* triplet state after a rapid intersystem crossing (ISC) process (7.6 ps), leading to the generation of phenyl radicals on the picosecond time scale. Compared with Benzoin, DMB possesses two methoxy groups which are able to stabilize the alcohol radical and thus result in a stronger driving force for cleavage and a higher quantum yield of photodissociation. Two stable conformations (cis-DMB and trans-DMB) at ground state were found via DFT calculations. The influence of the intramolecular hydrogen bond on the α-cleavage of DMB was elaborated.

The role of the metal ion in the photophysical behavior of Co(II), Ni(II), and Cu(II) octabutoxynaphthalocyanines: insights from ultra-fast time-resolved spectroscopy and DFT/TDDFT calculations

2010 ◽  
Vol 14 (08) ◽  
pp. 689-700 ◽  
Author(s):  
Giampaolo Ricciardi ◽  
Alexandra V. Soldatova ◽  
Angela Rosa
Keyword(s):  
Density Functional Theory ◽  
Metal Ion ◽  
Density Functional ◽  
Transient Absorption ◽  
Density Functional Theory Calculations ◽  
Fast Time ◽  
Central Metal ◽  
Functional Theory ◽  
Time Resolved ◽  
Deactivation Mechanism

The photo-deactivation mechanism of the MNc(OBu)8 (M = Co, Ni, Cu) series of complexes is reviewed, with special emphasis on the role played by the central metal. Ultra-fast transient absorption experiments and Density Functional Theory and time-dependent Density Functional Theory calculations consistently show that the central metal modifies the photo-deactivation mechanism of the investigated complexes by inducing substantial changes in the nature and energy of the excited states lying between the photo-generated state and the ground state.

scholarly journals Ground- and excited-state characteristics in photovoltaic polymer N2200

RSC Advances ◽  
2021 ◽  
Author(s):  
Guanzhao Wen ◽  
Xianshao Zou ◽  
Rong Hu ◽  
Jun Peng ◽  
Zhifeng Chen ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Excited State ◽  
Steady State ◽  
Excited States ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Time Dependent ◽  
Functional Theory ◽  
Time Resolved ◽  
Dependent Density

Ground- and excited-states properties of N2200 have been studied by steady-state and time-resolved spectroscopies as well as time-dependent density functional theory calculations.

Density Functional Theory Study of Uranium(VI) Aquo Chloro Complexes in Aqueous Solution

2008 ◽  
Vol 112 (11) ◽  
pp. 2428-2436 ◽  
Author(s):  
Michael Bühl ◽  
Nicolas Sieffert ◽  
Volodymyr Golubnychiy ◽  
Georges Wipff
Keyword(s):  
Aqueous Solution ◽  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Chloro Complexes
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