Experimental and Calculated Spectra of 蟺-Stacked Mild Charge-Transfer Complexes: Jet-Cooled Perylene路(Tetrachloroethene)n, n = 1,2
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- 作者：Franziska A. Balmer ; Philipp Ottiger ; Samuel Leutwyler
- 刊名：Journal of Physical Chemistry A
- 出版年：2015
- 出版时间：October 22, 2015
- 年：2015
- 卷：119
- 期：42
- 页码：10462-10474
- 全文大小：641K
- ISSN：1520-5215
文摘
The S0 鈫?S1 spectra of the mild charge-transfer (CT) complexes perylene路tetrachloroethene (P路4ClE) and perylene路(tetrachloroethene)2 (P路(4ClE)2) are investigated by two-color resonant two-photon ionization (2C-R2PI) and dispersed fluorescence spectroscopy in supersonic jets. The S0 鈫?S1 vibrationless transitions of P路4ClE and P路(4ClE)2 are shifted by 未谓 = 鈭?51 and 鈭?58 cm鈥? relative to perylene, translating to excited-state dissociation energy increases of 5.4 and 10.3 kJ/mol, respectively. The red shift is 鈭?0% larger than that of perylene路trans-1,2-dichloroethene; therefore, the increase in chlorination increases the excited-state stabilization and CT character of the interaction, but the electronic excitation remains largely confined to the perylene moiety. The 2C-R2PI and fluorescence spectra of P路4ClE exhibit strong progressions in the perylene intramolecular twist (1au) vibration (42 cm鈥? in S0 and 55 cm鈥? in S1), signaling that perylene deforms along its twist coordinate upon electronic excitation. The intermolecular stretching (Tz) and internal rotation (Rc) vibrations are weak; therefore, the P路4ClE intermolecular potential energy surface (IPES) changes little during the S0 鈫?S1 transition. The minimum-energy structures and inter- and intramolecular vibrational frequencies of P路4ClE and P路(4ClE)2 are calculated with the dispersion-corrected density functional theory (DFT) methods B97-D3, 蠅B97X-D, M06, and M06-2X and the spin-consistent-scaled (SCS) variant of the approximate second-order coupled-cluster method, SCS-CC2. All methods predict the global minima to be 蟺-stacked centered coplanar structures with the long axis of tetrachloroethene rotated by 蟿 鈮?60掳 relative to the perylene long axis. The calculated binding energies are in the range of 鈭?i>D0 = 28鈥?5 kJ/mol. A second minimum is predicted with 蟿 鈮?25掳, with 鈭? kJ/mol smaller binding energy. Although both monomers are achiral, both the P路4ClE and P路(4ClE)2 complexes are chiral. The best agreement for adiabatic excitation energies and vibrational frequencies is observed for the 蠅B97X-D and M06-2X DFT methods.