Università di Bologna, Dipartimento di Chimica 'G. Ciamician', Via F. Selmi, 2, 40126 Bologna, Italy.
MEDITEKNOLOGY srl, Via P. Gobetti 101, 40129 Bologna, Italy.
Photochem Photobiol Sci. 2019 Sep 1;18(9):2180-2190. doi: 10.1039/c9pp00006b. Epub 2019 Feb 28.
The one-photon (1P) and two-photon (2P) absorption properties of three quadrupolar dyes, featuring thiophene as a donor and acceptors of varying strengths, are determined by a combination of experimental and computational methods employing the density functional theory (DFT). The emission shifts in different solvents are well reproduced by time-dependent DFT calculations with the linear response and state specific approaches in the framework of the polarizable continuum model. The calculations show that the energies of both 1P- and 2P-active states decrease with an increase of the strength of the acceptor. The 2P absorption cross-sections predicted by the response theory are accounted for by considering just one intermediate state (S) in the sum-over-states formulation. For the chromophore featuring the stronger acceptor, the energetic positions of the 1P- and 2P-active states prevent the exploitation of the theoretically predicted very high 2P activity due to the competing 1P absorption into the S state.
三种四极染料的单光子（1P）和双光子（2P）吸收特性，通过组合使用密度泛函理论（DFT）的实验和计算方法来确定，这些染料的供体为噻吩，受体的强度不同。采用极化连续体模型的线性响应和状态特定方法，通过时间相关的 DFT 计算可以很好地重现不同溶剂中的发射位移。计算表明，1P-和 2P-活性态的能量随受体强度的增加而降低。在状态求和公式中仅考虑一个中间态（S），即可解释响应理论预测的 2P 吸收截面。对于具有较强受体的生色团，由于 1P 吸收进入 S 态，1P-和 2P-活性态的能量位置阻止了理论上预测的非常高的 2P 活性的利用。
