A theoretical forecast of the hydrogen bond changes in the electronic excited state for BN and its derivatives

Abstract

Ê Ú ¼ ÖÙ ÖÝ ¾¼½½ ÔØ ¼ Ù Ù×Ø ¾¼½½ ×ØÖ ØThe relationship between electronic spectral shifts and hydrogen-bonding dynamics in electronically excited states of the hydrogen-bonded complex is put forward. Hydrogen bond strengthening will induce a redshift of the corresponding electronic spectra, while hydrogen bond weakening will cause a blueshift. Time-dependent density function theory (TDDFT) was used to study the excitation energies in both singlet and triplet electronically excited states of Benzonitrile (BN), 4-aminobenzonitrile (ABN), and 4-dimethylaminobenzonitrile (DMABN) in methanol solvents. Only the intermolecular hydrogen bond C≡N· · · H-O was involved in our system. A fairly accurate forecast of the hydrogen bond changes in lowlying electronically excited states were presented in light of a very thorough consideration of their related electronic spectra. The deduction we used to depict the trend of the hydrogen bond changes in excited states could help others understand hydrogen-bonding dynamics more effectively.

The Role of H-Bonds in the Excited-State Properties of Multichromophoric Systems: Static and Dynamic Aspects

“…These first findings by Zhao et al paved the way for numerous other theoretical and experimental studies to understand how the electronic properties of different chromophores are modified when H-bonding interactions are involved [3,25,37,94,95]. For example, Wang et al theoretically investigated the low-lying electronic excited states of the benzonitrile (BN) molecule and its derivatives as hydrogen bond acceptors in a hydrogen-donating MeOH solvent [3]. Additionally, the spectral features of fluorenone (FN) molecules in MeOH (Figure 1e) could be explained by a change in the strength of the intermolecular H-bond between FN and solvent molecules upon photoexcitation [37].…”

“…This led to the conclusion that, in this case, the intermolecular H-bond should be weakened in the T 1 and S 1 states and strengthened in the S 2 state. These first findings by Zhao et al paved the way for numerous other theoretical and experimental studies to understand how the electronic properties of different chromophores are modified when H-bonding interactions are involved [3,25,37,94,95]. For example, Wang et al theoretically investigated the low-lying electronic excited states of the benzonitrile (BN) molecule and its derivatives as hydrogen bond acceptors in a hydrogen-donating MeOH solvent [3].…”

“…On the other hand, it has been proved that intermolecular H-bonds can significantly facilitate internal conversions, intersystem crossing, and intramolecular charge transfers [3,35].…”

“…Their intrinsic nature suggests that H-bonds can be suitably exploited to tune the static and dynamic properties of electronic states in complex multichromophoric systems. Therefore, the nature of H-bonds and how their presence might affect the structural and electronic properties of these systems have been the subject of intense investigations by different experimental and theoretical methods [1][2][3][4][5][6][7][8].…”

Cooperative Excited-State Hydrogen Bond Strengthening and Weakening and Concerted Excited-State Proton Transfer and Twisted Intramolecular Charge Transfer of Thiazolidinedione Derivatives in Solution

“…What's more, it has been demonstrated that both the excited-state hydrogen bond strengthening and weakening play very significant roles in the processes of internal conversion (IC) [13], electronic spectral shifts (ESS) [12], photoinduced electron transfer (PET) [14], intramolecular charge transfer (ICT) [15,16], and metal-to-ligand charge transfer (MLCT) [17,18], and so on. It is important to mention that an effective rule, illustrating and inferring excited-state hydrogen bonding strengthening or weakening via an electronic spectral red-shift or blue-shift, have been presented recently [12,19], and the effective rule has been taken into account to explain the experiment by other groups [20][21][22][23][24][25][26]. A great deal of the studies have been focused on the hydrogen bonding dynamics, however, it is still desirable to carry out further works dealing with the effect of the excited-state hydrogen bonding dynamics on the photochemistry, photophysics and photobiology.…”