State-resolved dynamics study of the H + HS reaction on the A' and A″ states with time-dependent quantum wave packet method.

The quantum dynamics calculations of the H + HS (v = 0, j = 0) reaction on the A' and A″ potential energy surfaces (PESs) are performed using the reactant coordinate based time-dependent wave packet method. State-averaged and state-resolved results for both channels of the title reaction are presented in the 0.02-1.

Non-adiabatic dynamics investigation of the radiationless decay mechanism of trans-urocanic acid in the S2 state.

The trans-urocanic acid, a UV chromophore in the epidermis of human skin, was found to exhibit a wavelength dependent isomerization property. The isomerization quantum yield to cis-urocanic is greatest when being excited to the S1 state, whereas exciting the molecule to the S2 state causes almost no isomerization. The comparative photochemical behavior of the trans-urocanic on the S1 and S2 states continues to be the subject of intense research effort.

Photophysical Properties of a Post-Self-Assembly Host/Guest Coordination Cage: Visible Light Driven Core-to-Cage Charge Transfer.

Supramolecular systems are capable of unique photophysical properties due to possible interactions between subcomponents, such as between an encapsulated molecule and its cage in a host/guest environment. Here, we report that the encapsulation of a chromophore by a metallacage dramatically enhances its photophysical properties. In the visible region, the encapsulated photosensitizer achieves a 6.

Steady-state and time-resolved spectroscopic investigations on the existence of stable methanol/AOT/n-heptane reverse micelles.

In this work, we have reported our study on the controversial issue whether methanol molecules can be effectively encapsulated by surfactant AOT to form true reverse micelles. We compared the different photophysical properties of coumarin 153 (C153) in methanol/AOT/n-heptane reverse micelles and methanol/n-heptane binary mixture by means of steady-state absorption, fluorescence and time-resolved fluorescence spectroscopies. In the reverse micelles, the fluorescence emission spectra of C153 were dependent on the excitation wavelength, while in binary mixtures, the excitation wavelength dependence was not observed.

Photophysical properties of self-assembled multinuclear platinum metallacycles with different conformational geometries.

In this work, spectroscopic techniques and quantum chemistry calculations were used to investigate the photophysical properties of various multinuclear platinum complexes with different conformational geometries. This suite of complexes includes a Pt-pyridyl square, a Pt-carboxylate triangle, and a mixed Pt-pyridyl-carboxylate rectangle, as well as two mononuclear Pt model complexes. Studying the individual molecular precursors in the context of larger assemblies is important to provide a complete understanding of the factors governing the observed photophysical properties of a given system.

Experimental and theoretical study on the photophysical properties of 90° and 60° bimetallic platinum complexes.

The 90° and 60° bimetallic platinum complexes with special structures are widely used in coordination-driven self-assembled metallosupramolecular architectures, and these complexes are the key components of triangular, rectangular, and polygonal metallacycle and metallocage supramolecules. Therefore, spectroscopic techniques and quantum chemistry calculations were employed in this article to investigate the photophysical properties of these bimetallic platinum complexes. Compared with spectra for the ligands, the absorption spectra of these Pt complexes are red-shifted, and the fluorescence spectra become wider and are also red-shifted.

Steered molecular dynamics simulation study on dynamic self-assembly of single-stranded DNA with double-walled carbon nanotube and graphene.

In the present work, we explored the diameter selectivity of dynamic self-assembly for the single-strand DNA (ssDNA) encapsulation in double-walled nanotubes (DWNTs) via molecular dynamics simulation method. Moreover, the pulling out process was carried out by steered molecular dynamics simulations. Considering π-π stacking and solvent accessibility together, base-CNT binding should be strongest on a graphene sheet and weakest on the inner CNT surface.

Modification of n-type organic semiconductor performance of perylene diimides by substitution in different positions: two-dimensional π-stacking and hydrogen bonding.

Perylene diimides (PDIs) and their derivatives are active n-type semiconducting materials widely used in organic electronic devices. A series of PDI derivatives have been investigated by quantum chemistry calculations combined with Marcus-Hush electron-transfer theory. The substitution of three different sites of a PDI induces large changes in its electron-transfer mobility.

Molecular dynamics simulation exploration of unfolding and refolding of a ten-amino acid miniprotein.

Steered molecular dynamics simulations are performed to explore the unfolding and refolding processes of CLN025, a 10-residue beta-hairpin. In unfolding process, when CLN025 is pulled along the termini, the force-extension curve goes back and forth between negative and positive values not long after the beginning of simulation. That is so different from what happens in other peptides, where force is positive most of the time.

Hydrogen bonding in the electronic excited state.

Because of its fundamental importance in many branches of science, hydrogen bonding is a subject of intense contemporary research interest. The physical and chemical properties of hydrogen bonds in the ground state have been widely studied both experimentally and theoretically by chemists, physicists, and biologists. However, hydrogen bonding in the electronic excited state, which plays an important role in many photophysical processes and photochemical reactions, has scarcely been investigated.

Substituent effects on the intramolecular charge transfer and fluorescence of bimetallic platinum complexes.

An investigation of a series of platinum-containing organometallic complexes for the study of fluorescence phenomena in organometallic chromophores controlled by the intramolecular charge transfer (ICT) is presented in this work. We report steady-state and time-resolved spectroscopic experiments as well as quantum chemistry calculations to investigate the substituent effects on the ICT and fluorescence emission. We demonstrate that the fluorescence maximum and lifetimes greatly depend on different substituents and the presence of bimetallic platinum donor.

A TD-DFT study on the cyanide-chemosensing mechanism of 8-formyl-7-hydroxycoumarin.

Proton transfer (PT) and excited-state PT process are proposed to account for the fluorescent sensing mechanism of a cyanide chemosensor, 8-formyl-7-hydroxycoumarin. The time-dependent density functional theory method has been applied to investigate the ground and the first singlet excited electronic states of this chemosensor as well as its nucleophilic addition product with cyanide, with a view to monitoring their geometries and spectrophotometrical properties. The present theoretical study indicates that phenol proton of the chemosensor transfers to the formyl group along the intramolecular hydrogen bond in the first singlet excited state.

The effect of intermolecular hydrogen bonding on the fluorescence of a bimetallic platinum complex.

The bimetallic platinum complexes are known as unique building blocks and arewidely utilized in the coordination-driven self-assembly of functionalized supramolecular metallacycles. Hence, photophysical study of the bimetallic platinum complexes will be very helpful for the understanding on the optical properties and further applications of coordination-driven self-assembled supramolecular metallacycles. Herein, we report steady-state and time-resolved spectroscopic experiments as well as quantum chemistry calculations to investigate the significant intermolecular hydrogen bonding effects on the intramolecular charge transfer (ICT) fluorescence of a bimetallic platinum compound 4,4'-bis(trans-Pt(PEt(3))(2)OTf)benzophenone 3 in solution.

pH-Controlled twisted intramolecular charge transfer (TICT) excited state via changing the charge transfer direction.

In this work, a new model compound, the twisted intramolecular charge transfer (TICT) excited state of Milrinone (MIR), has been theoretically presented. MIR exists in different tautomeric and ionic forms in aqueous solution with different pH values. The TICT excited state properties for various forms of MIR are demonstrated to be significantly different and controlled by the pH values of MIR in aqueous solution.

Photophysical properties of coordination-driven self-assembled metallosupramolecular rhomboids: experimental and theoretical investigations.

In this work, the photophysical properties of coordination-driven self-assembled metallosupramolecular rhomboids with the donor ligands 1,2-bis(3-pyridyl)ethyne (3a) and 1,4-bis(3-pyridyl)-1,3-butadiyne (3b) are investigated by use of both spectroscopic experiments and quantum chemistry calculations. All the geometric conformations of the chair and boat conformers of 3a and 3b are fully optimized using density functional theory. The time-dependent density functional theory method was also used to study the excited-state properties of these self-assembled metallosupramolecular rhomboids.

TD-DFT study on the sensing mechanism of a fluorescent chemosensor for fluoride: excited-state proton transfer.

An excited-state proton transfer (ESPT) process, induced by both intermolecular and intramolecular hydrogen-bonding interactions, is proposed to account for the fluorescence sensing mechanism of a fluoride chemosensor, phenyl-1H-anthra(1,2-d)imidazole-6,11-dione. The time-dependent density functional theory (TD-DFT) method has been applied to investigate the different electronic states. The present theoretical study of this chemosensor, as well as its anion and fluoride complex, has been conducted with a view to monitoring its structural and photophysical properties.

Theoretical Insights into Hydrogen Bonding and Its Influence on the Structural and Spectral Properties of Aquo Palladium(II) Complexes: cis-[(dppp)Pd(H2O)2](2+), cis-[(dppp)Pd(H2O)(OSO2CF3)](+)(OSO2CF3)(-), and cis-[(dppp)Pd(H2O)2](2+)(OSO2CF3)(-)2.

Density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods have been performed to investigate the ground and excited states of aquo palladium(II) complexes cis-[(dppp)Pd(H2O)2](2+), cis-[(dppp)Pd(H2O)(OSO2CF3)](+)(OSO2CF3)(-), and cis-[(dppp)Pd(H2O)2](2+)(OSO2CF3)(-)2. Insights into the influence of hydrogen bonding on the structural and spectral properties of these three aquo Pd(II) complexes are presented. The structures and the HOMO-LUMO energy gap of the three aquo Pd(II) complexes can be markedly influenced by hydrogen bonding interactions.

Role of intramolecular and intermolecular hydrogen bonding in both singlet and triplet excited states of aminofluorenones on internal conversion, intersystem crossing, and twisted intramolecular charge transfer.

Time-dependent density functional theory method was performed to investigate the intramolecular and intermolecular hydrogen bonding in both the singlet and triplet electronic excited states of aminofluorenones AF, MAF, and DMAF in alcoholic solutions as well as their important roles on the excited-state photophysical processes of these aminofluorenones, such as internal conversion, intersystem crossing (ISC), twisted intramolecular charge transfer (TICT), and so forth. The intramolecular hydrogen bond C=O..

Reconsideration of the excited-state double proton transfer (ESDPT) in 2-aminopyridine/acid systems: role of the intermolecular hydrogen bonding in excited states.

In the present work, the excited-state double proton transfer (ESDPT) in 2-aminopyridine (2AP)/acid systems has been reconsidered using the combined experimental and theoretical methods. The steady-state absorption and fluorescence spectra of 2AP in different acids, such as formic acid, acetic acid, propionic acid, etc. have been measured.

Excited state electronic structures and photochemistry of heterocyclic annulated perylene (HAP) materials tuned by heteroatoms: S, Se, N, O, C, Si, and B.

Time-dependent density functional theory (TDDFT) method was performed to investigate the excited state electronic structures and photochemistry of a variety of heterocyclic annulated perylene (HAP) materials. The calculated electronic structures and photochemical properties of the newly synthesized S-, Se-, and N-heterocyclic annulated perylenes were in good agreement with the experimental results. Moreover, the O-, C-, Si-, and B-heterocyclic annulated perylenes were also theoretically designed and investigated by using the same computational methods in this work.

Photoinduced intramolecular charge transfer and S2 fluorescence in thiophene-pi-conjugated donor-acceptor systems: experimental and TDDFT studies.

Experimental and theoretical methods were used to study newly synthesized thiophene-pi-conjugated donor-acceptor compounds, which were found to exhibit efficient intramolecular charge-transfer emission in polar solvents with relatively large Stokes shifts and strong solvatochromism. To gain insight into the solvatochromic behavior of these compounds, the dependence of the spectra on solvent polarity was studied on the basis of Lippert-Mataga models. We found that intramolecular charge transfer in these donor-acceptor systems is significantly dependent on the electron-withdrawing substituents at the thienyl 2-position.

Time-dependent density functional theory study on hydrogen-bonded intramolecular charge-transfer excited state of 4-dimethylamino-benzonitrile in methanol.

The time-dependent density functional theory (TDDFT) method was carried out to investigate the hydrogen-bonded intramolecular charge-transfer (ICT) excited state of 4-dimethylaminobenzonitrile (DMABN) in methanol (MeOH) solvent. We demonstrated that the intermolecular hydrogen bond C[triple bond]N..

Site-specific solvation of the photoexcited protochlorophyllide a in methanol: formation of the hydrogen-bonded intermediate state induced by hydrogen-bond strengthening.

The site-specific solvation of the photoexcited protochlorophyllide a (Pchlide a) in methanol solvent was investigated using the time-dependent density functional theory method for the first time to our knowledge. The intermolecular site-specific coordination and hydrogen-bonding interactions between Pchlide a and methanol molecules play a very important role in the steady-state and time-resolved spectra. All the calculated absorption and fluorescence spectra of the isolated Pchlide a and its coordinated and hydrogen-bonded complexes with methanol demonstrate that the novel fluorescence shoulder at approximately 690 nm of Pchlide a in methanol should be ascribed to the coordinated and hydrogen-bonded Pchlide a-(MeOH)(4) complex.

Ultrafast excited-state dynamics of tetraphenylethylene studied by semiclassical simulation.

Detailed simulation study is reported for the excited-state dynamics of photoisomerization of cis-tetraphenylethylene (TPE) following excitation by a femtosecond laser pulse. The technique for this investigation is semiclassical dynamics simulation, which is described briefly in the paper. Upon photoexcitation by a femtosecond laser pulse, the stretching motion of the ethylenic bond of TPE is initially excited, leading to a significant lengthening of ethylenic bond in 300 fs.