利用B3LYP方法优化了多吡啶钌乙炔配合物[(tpy)(bpy)RuC≡CC6H4R]+[tpy=2,2′:6′,2"-terpyridine,bpy=2,2′-bipyridine;R=Cl(1),H(2),OMe(3)]的基态几何结构,得到的几何参数与实验结果吻合。利用SCRF方法中的CPCM模型来模拟溶剂化效应,采用TDDFT(Time-Dependent Density Functional Theory)方法计算得到了配合物在CH3CN溶液中的激发态电子结构和电子吸收光谱。研究结果表明,配合物1~3溶液吸收光谱的跃迁性质相似,其中低能吸收均被指认为MLCT和LLCT混合激发跃迁。
A series of ruthenium(II) complexes Ru(fppz)2(CO)L [fppz = 3-trifluoromethyl-5(2-pyridyl)pyrazole; L = pyridine (1), 4-dimethylaminopyridine (2), 4-cyanopyridine (3)] were designed and investigated theo-retically to explore their electronic structures, absorption, and emissions as well as the solvatochrom-ism. The singlet ground state and triplet excited state geometries were fully optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ level, respectively. The HOMO of 1-3 is composed of dyz(Ru) atom and π(fppz). The LUMO of 1 and 2 is dominantly contributed by π*(fppz) orbital, but that of 3 is con-tributed by π*(L). Absorption and phosphorescence in vacuo, C6H12, and CH3CN media were calculated using the TD-DFT level of theory with the PCM model based on the optimized ground and excited state geometries, respectively. The lowest-lying absorption of 1 and 2 at 387 and 391 nm is attributed to {[dyz(Ru) + π(fppz)] → [π*(fppz)]} transition, but that of 3 at 479 nm is assigned to {[dyz(Ru) + π(fppz)] → [π*(L)]} transition. The phosphorescence of 1 and 2 at 436 and 438 nm originates from 3{[dyz(Ru) + π(fppz)] [π*(fppz)]} excited state, while that of 3 at 606 nm is from 3{[dyz(Ru) + π(fppz)] [π*(L)]} excited state. The calculation results showed that the absorption and emission transition character can be changed from MLCT/ILCT to MLCT/LLCT transition by altering the substituent on the L ligand. The phosphorescence of 1 and 2 does not have solvatochromism, but that of 3 at 606 nm (vacuo), 584 nm (C6H12), and 541 nm (CH3CN) is strongly dependent on the solvent polarity, so introducing elec-tron-withdrawing group on ligand L will induce remarkable solvatochromism.
LIU Tao1, ZHOU Xin1, BAI FuQuan1, ZHANG JianPo1, XIA BaoHui1,2, PAN QingJiang3 & ZHANG HongXing1 1 State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, China
A variety of heteroleptic ruthenium sensitizers have been engineered and synthesized because of their higher light-harvesting efficiency and lower charge-recombination possibility than the well known homoleptic N3 dye.As such,a great deal of attention has been focused on sensitizers with the general formula Ru(ancillary-ligand)(anchoring-ligand)(NCS) 2,among which important examples are Ru(4,4'-bis(5-hexylthiophen-2-yl)-2,2'-bipyridine)(4,4'-carboxylic acid-4'-2,2'-bipyridine)(NCS)2(C101) and Ru(N-(4-butoxyphenyl)-N-2-pyridinyl-2-pyridinamine)(4,4'-carboxylic acid-4'-2,2'-bipyridine)(NCS)2(J13).In order to simulate experimental conditions with different pH values,the photosensitizing processes of these sensitizers possessing different degrees of deprotonation (2H,1H to 0H) have been explored theoretically in this work.Their ground/excited state geometries,electronic structures and spectroscopic properties are first calculated using density functional theory (DFT) and time-dependent DFT (TDDFT).The absorption and emission spectra of all the complexes in acetonitrile solution are also predicted at the TDDFT (B3LYP) level.The calculated results show that the ancillary ligand contributes to the molecular orbital (MO) energy levels and absorption transitions.It is intriguing to observe that the introduction of a thiophene group into the ancillary ligand leads directly to the increased energy of the absorption transitions in the 380-450 nm region.The calculations reveal that although deprotonation destabilizes the overall frontier MOs of the chromophores,it tends to exert a greater influence on the unoccupied orbitals than on the occupied orbitals.Consequently,an obvious blue shift was observed for the absorptions and emissions in going from 2H,1H to 0H.Finally,the optimal degree of deprotonation for C101 and J13 has also been evaluated,which is expected to lead to further improvements in the performance of dye-sensitized solar cells (DSSCs) coated with such sensitizers.
