DFT/TDDFT investigation on bis-cyclometalated alkynylgold(III) complex: Comparison of absorption and emission properties

absorption and phosphorescent mechanism of three Au(III) complexes, Au(2,5-F2C6H3-C^C^C)(C≡C-C6H4N(C6H5)2 [Au25FPh], Au(3,5-F2C6H3-C^C^C)(C≡C-C6H4N(C6H5)2 [Au35FPh], and Au(3,5-F2C6H3-C^C^C)(C≡C-C6H4N(1H-indole)2 [Au35FID], are calculated and compared using density functional theory (DFT) and time-dependent DFT (TDDFT). The calculated results reveal that enlarging the center C^C^C ligand will result in the enhanced LMCT participation. This theoretical contribution allows design of new Au(Ⅲ) complexes with higher phosphorescence efficiency.     

Theoretical studies on Ru(fppz)2(CO)L (L = N -heterocyclic ligand): Electronic structure, absorption, phosphorescence, and solvatochromism

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 theoretically to explore their electronic structures, absorption, and emissions as well as the solvatochromism. 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 d_yz(Ru) atom and π(fppz). The LUMO of 1 and 2 is dominantly contributed by π*(fppz) orbital, but that of 3 is contribute 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 {[d_yz(Ru) + π(fppz)] → [π*(fppz)]} transition, but that of 3 at 479 nm is assigned to {[d_yz(Ru) + π(fppz)] → [π*(L)]} transition. The phosphorescence of 1 and 2 at 436 and 438 nm originates from ³{[d_yz(Ru) + π(fppz)] [π*(fppz)]} excited state, while that of 3 at 606 nm is from ³{[d_yz(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 electron-withdrawing group on ligand L will induce remarkable solvatochromism. Supported by the National Natural Science Foundation of China (Grant Nos. 20573042, 20703015, and 20333050)     

利用DFT方法探究一类自组装[Pt2M4（C≡CH）8]（M=Cu，Ag）簇合物的电子结构和光谱性质

应用TD．DFT（time－dependent density functional theory）并PCMfpolarizable continuum model）模型研究了一类自组装的[Pt2M4（C＇≡CH）8]（M=Cu,Ag）簇合物的电子结构和光谱性质．应用DFT（density functional theory）方法优化了该簇合物的基态及激发态结构．综合计算结果,得到与试验结果相一致的结构与光谱特点．[Pt2Ag4（C≡CH）8]具有呈D4和D4h对称性的两个稳定的基态几何结构．Pt－M距离预示弱相互作用的存在．Cu—Cu距离大于俩个Cu原子的范德华半径和而Ag－Ag间距与俩个Ag原子的范德华半径和差别不大．激发过程使得Pt…M,Ag…Ag作用增强,虽然Cu…Cu距离也相应缩短,但是其仍大于范德华半径之和．[Pt2Cu4（C≡CH）8]、[Pt2Ag4（C≡CH）8]（A）和（B）的最低能吸收在450、365和375nm处,发射在611、431和435nm处．红外可见谱范围内,[Pt2M4（C≡CH）8]的吸收波带都有Cu或Ag成分的贡献,所以没有ILCT或MPtLCT跃迁特征出现（ILCT：intraligand charge transfer;MLCT：metal-to—ligand charge transfer）．由于最低能吸收和发射具有不同的跃迁特征,所以发射不是来自于最低能吸收．[Pt2Ag4（C≡CH）8]簇合物的MM相互作用在激发态增强,发射光谱具有显著的ILCT特点,这也是[Pt2Ag4（C≡CH）8]的发射波长相对于其对应的同配体前躯体[Pt（C≡CH）4]^2-有少许蓝移的原因．     

DFT evaluation of the electronic structures and spectroscopic properties of the self-assembled [Pt2M4(C ≡ CH)8] (M=Cu,Ag) clusters

Science China Chemistry - Electronic structures and spectroscopic properties of self-assembled [Pt2M4(C≡CH)8] (M=Cu, Ag) clusters have been studied by the TD-DFT (time-dependent density...     

DFT and TDDFT investigations on the ground and excited states for polynuclear platinum(Ⅱ) complexes containing the rigid phenylacetylide ligand

We have studied the ground and excited states of the three dendritic polynuclear Pt(Ⅱ) complexes 1-[Cl(PH3)2PtC≡C]-3,5-[HC≡C]C6H3 (1), 1,3-[Cl(PH3)2PtC≡C]2-5-[HC≡C]C6H3 (2), and 1,3,5-[Cl(PH3)2- PtC≡C]3C6H3 (3), by using the B3LYP and UB3LYP methods, respectively. TDDFT approach with the PCM model was performed to predict the emission spectra properties of 1-3 in CH2Cl2 solution. We first predicted the excited-state geometries for the three complexes. With the change of the number of Pt(Ⅱ) atom, 1-3 show the different geometry structures in both the ground and excited states; furthermore, the increase of the metal density from 1 to 3 results in the red shift of the lowest-energy emissions along the series. The luminescent properties of 1 are somewhat different from those of 2 and 3. The emission properties of 2 and 3 are richer than 1. Our conclusion can give a good support for designing the high efficient luminescent materials.     

New progress of plasmonics in complex metal nanostructures

Noble metal nanostructures possess novel optical properties because of their collective electronic oscillations,known as surface plasmons(SPs).The resonance of SPs strongly depends on the material,surrounding environment,as well as the geometry of the nanostructures.Complex metal nanostructures have attracted research interest because of the degree of freedom in tailoring the plasmonic properties for more advanced applications that are unattainable by simple ones.In this review,we discuss the plasmonic properties of several typical types of complex metal nanostructures,that is,electromagnetically coupled nanoparticles(NPs),NPs/metal films,NPs/nanowires(NWs),NWs/NWs,and metal nanostructures supported or coated by dielectrics.The electromagnetic field enhancement and surface-enhanced Raman scattering applications are mainly discussed in the NPs systems where localized SPs have a key role.Propagating surface plasmon polaritons and relevant applications in plasmonic routers and logic gates using NWs network are also reviewed.The effect of dielectric substrates and surroundings of metal nanostructures to the plasmonic properties is also discussed.     

The emission positions of kHz QPOs and Kerr spacetime influence

Based the Alfven wave oscillation model (AWOM) and relativistic precession model (RPM) for twin kHz QPOs, we estimate the emission positions of most detected kHz QPOs to be at r=18+/−3 km (R/15 km), except Cir X-1 at r∼30+/−5 km (R/15 km). For the proposed Keplerian frequency as an upper limit to kHz QPO, the spin effects in Kerr Spacetime are discussed, which have about a 5% (2%) modification for that of the Schwarzchild case for the spin frequency of 1000 (400) Hz. The application to the four typical QPO sources, Cir X-1, Sco X-1, SAX J1808.4-3658 and XTE 1807-294, is mentioned.

     

Theoretical studies on the spectroscopic properties and the substituent effects of pyridyl triazole Os(II) complexes

To explore the spectroscopic properties of pyridyl triazole Os(II) complexes and how the substituent effects affect the spectroscopic properties of [Os(ptz)₂L₂] (L=PH₃; ptzH=(2-pyridyl)-1,2,4-triazole) (1), [Os(bptz)₂L₂] (bptzH=3-tert-butyl-5-(2-pyridyl)-1,2,4-triazole) (2), [Os(fptz)₂L₂] (fptzH=3-(trifluoreomethyl)-5-(2-pyridyl)-1,2,4-triazole) (3), and [Os(fbtz)₂L₂] (fbtzH=3-(trifluoreomethyl)-5-(4-tert-butyl- 2-pyridyl)-1,2, 4-triazole) (4), the density functional theory (DFT) method at the B3LYP level was used to optimize the geometrical structures in the ground and excited state. The absorption and emission properties of the dichloromethane solution were predicted at the time-dependent density functional theory (TD-DFT, B3LYP) level associated with the PCM solvent effect model, the transitions characters of them were assigned. Important correlations between substituent effects and emission spectra and the quantum yield have been obtained by comparing and analyzing the calculated results.     

Theoretical studies of the structures and spectroscopic properties of the photoelectrochemical cell ruthenium sensitizers, C101 and J13

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.     

DFT and TDDFT investigations on the ground and excited states for polynuclear platinum(II) complexes containing the rigid phenylacetylide ligand

We have studied the ground and excited states of the three dendritic polynuclear Pt(II) complexes 1-[Cl(PH3)2PtC≡≡ C]-3,5-[HC≡≡ C]C6H3 (1), 1,3-[Cl(PH3)2PtC≡≡ C]2-5-[HC≡≡ C]C6H3 (2), and 1,3,5-[Cl(PH3)2- PtC≡≡ C]3C6H3 (3), by using the B3LYP and UB3LYP methods, respectively. TDDFT approach with the PCM model was performed to predict the emission spectra properties of 1―3 in CH2Cl2 solution. We first predicted the excited-state geometries for the three complexes. With the change of the number of Pt(II) atom, 1―3 show the different geometry structures in both the ground and excited states; fur- thermore, the increase of the metal density from 1 to 3 results in the red shift of the lowest-energy emissions along the series. The luminescent properties of 1 are somewhat different from those of 2 and 3. The emission properties of 2 and 3 are richer than 1. Our conclusion can give a good support for designing the high efficient luminescent materials.