Mononuclear Copper(I) 3-(2-pyridyl)pyrazole Complexes: The Crucial Role of Phosphine on Photoluminescence

A series of emissive Cu(I) cationic complexes with 3-(2-pyridyl)-5-phenyl-pyrazole and various phosphines: dppbz (1), Xantphos (2), DPEPhos (3), PPh₃ (4), and BINAP (5) were designed and characterized. Complexes obtained exhibit bright yellow-green emission (ca. 520–650 nm) in the solid state with a wide range of QYs (1–78%) and lifetimes (19–119 µs) at 298 K. The photoluminescence efficiency dramatically depends on the phosphine ligand type. The theoretical calculations of buried volumes and excited states explained the emission behavior for 1–5 as well as their lifetimes. The bulky and rigid phosphines promote emission efficiency through the stabilization of singlet and triplet excited states.     

Organic triplet emissions of arylacetylide moieties harnessed through coordination to [Au(PCy(3))]+. Effect of molecular structure upon photoluminescent properties

A family of mono- and binuclear Cy(3)P-supported gold(I) complexes containing various pi-conjugated linear arylacetylide ligands, including the two homologous series (Cy(3)P)Au(Ctbd1;CC(6)H(4))(n)()(-)(1)(Ctbd1;CPh) and (Cy(3)P)Au(Ctbd1;CC(6)H(4))(n)()Ctbd1;CAu(PCy(3)) (n = 1-4), have been prepared. X-ray crystal analyses revealed no intermolecular aurophilic interactions in their crystal lattice. The lowest-energy singlet transitions are predominately intraligand in nature and exhibit both phenyl and acetylenic (1)(pipi) character. Strong photoluminescence is detected in solid and solution states under ambient conditions, with lifetimes in the microsecond regime. For complexes with a single arylacetylide group, only phosphorescence from the arylacetylide (3)(pipi) state is observed. Vibrational spacings in the solid-state emission spectra can be attributed to a combination of phenyl ring deformation and symmetric phenyl ring and Ctbd1;C stretches. Additional delayed-fluorescence emission is recorded for complexes with multiple p-arylacetylide units, and this is attributed to a triplet-triplet annihilation process. The phosphorescence energy of these complexes are readily modified by altering the length of the conjugated arylacetylide system, while the intensity of phosphorescence relative to fluorescence decreases when the p-arylacetylide chain is elongated. Information regarding the nature and relative energies of arylacetylide singlet and triplet excited states has been derived from the two homologous series and extrapolated to polymeric arylacetylide species. The (3)(pipi) excited-state reduction potentials E degrees [Au(+)/Au] (Au = 1a, 2, and 4) are estimated to be -1.80, -1.28, and -1.17 V versus SSCE, respectively.     

Study of the chemistry of ortho- and para-biphenylnitrenes by laser flash photolysis and time-resolved IR experiments and by B3LYP and CASPT2 calculations

The photochemistry of ortho-biphenyl azide (1a) has been studied by laser flash photolysis (LFP), with UV-vis and IR detection of the transient intermediates formed. LFP (266 nm) of 1a in glassy 3-methylpentane at 77 K releases singlet ortho-biphenylnitrene (1b) (lambda(max) = 410 nm, tau = 59 +/- 6 ns), which under these conditions decays cleanly to the lower energy triplet state. In fluid solution at 298 K, 1b rapidly (tau < 10 ns) partitions between formation of isocarbazole (4) (lambda(max) = 430 nm, tau = 70 ns) and benzazirine (1e) (lambda(max) = 305 nm, tau = 12 ns). Isocarbazole 4 undergoes a 1,5-hydrogen shift, with k(H)/k(D) = 3.4 at 298 K to form carbazole 9 and smaller amounts of two other isocarbazoles (7 and 8). Benzazirine 1e ring-opens reversibly to azacycloheptatetraene (1f), which serves as a reservoir for singlet nitrene 1b. Azacycloheptatetraene 1f ultimately forms carbazole 9 on the millisecond time scale by the pathway 1f --> 1e --> 1b --> 4 --> 9. The energies of the transient intermediates and of the transition structures connecting them were successfully predicted by CASPT2/6-31G calculations. The electronic and vibrational spectra of the intermediates, computed by density functional theory, support the assignment of the transient spectra, observed in the formation of 9 from 1a.     

Ligand-Localized Triplet-State Photophysics in a Platinum(II) Terpyridyl Perylenediimideacetylide

The synthesis, electrochemistry, and photophysical behavior of a Pt(II) terpyridyl perylenediimide (PDI) acetylide (1) charge-transfer complex is reported. The title compound exhibits strong (ε ≈ 5 × 10(4) M(-1)cm(-1)) low-energy PDI acetylide-based π-π* absorption bands in the visible range extending to 600 nm, producing highly quenched singlet fluorescence (Φ = 0.014 ± 0.001, τ = 109 ps) with respect to a nonmetalated PDI model chromophore. Nanosecond transient absorption spectroscopy revealed the presence of a long excited-state lifetime (372 ns in 2-methyltetrahydrofuran) with transient features consistent with the PDI-acetylide triplet state, ascertained by direct comparison to a model Pt(II) PDI-acetylide complex lacking low-energy charge-transfer transitions. For the first time, time-resolved step-scan FT-IR spectroscopy was used to characterize the triplet excited state of the PDI-acetylide sensitized in the title compound and its associated model complex. The observed red shifts (～30-50 cm(-1)) in the C═O and C≡C vibrations of the two Pt(II) complexes in the long-lived excited state are consistent with formation of the (3)PDI acetylide state and found to be in excellent agreement with the expected change in the relevant DFT-calculated IR frequencies in the nonmetalated PDI model chromophore (ground singlet state and lowest triplet excited state). Formation of the PDI triplet excited state in the title chromophore was also supported by sensitization of the singlet oxygen photoluminescence centered at ～1275 nm in air-saturated acetonitrile solution, Φ((1)O(2)) = 0.52. In terms of light emission, only residual PDI-based red fluorescence could be detected and no corresponding PDI-based phosphorescence was observed in the visible or NIR region at 298 or 77 K in the Pt(II) terpyridyl perylenediimideacetylide.     

Photochemistry of 4-(2-nitrophenyl)-1,4-dihydropyridines. Evidence for electron transfer and formation of an intermediate

New evidence about the path followed in the photochemical reaction of 4-(2-nitrophenyl)-1,4-dihydropyridines such as the drugs nifedipine (Compound 1) and nisoldipine (Compound 2) to give the corresponding nitrosophenylpyridines has been found through determination of the steady-state photochemical parameters and a comparison of the photoreactions in solution and in matrix at 90 K. Additional support is given by comparison with the isomeric 4-(3-nitrophenyl)dihydropyridine as well as with simpler derivatives, such as the corresponding 4-methyldihydropyridine. In Compounds 1 and 2, the lowest lying singlet, localized on the dihydropyridine chromophore, is deactivated by (largely exothermic) electron transfer to the nitrobenzene moiety, as evidenced by the complete quenching of the blue fluorescence observed in analogues not containing the electron-accepting group. Intramolecular proton transfer ensues in the 2-nitrophenyl derivatives with a relatively medium-independent quantum yield of approximately 0.3 and leads to an aromatic zwitterion, which is detected in matrix at 90 K (photoionization of this intermediate takes place in 2-methyltetrahydrofuran secondary). The intermediate is smoothly converted into the end product upon melting the glass. The 3-nitrophenyl analog, for which such a path is not available, is less reactive by about three orders of magnitude at 366 nm, although the quantum yield arrives at approximately 0.01 by irradiation at 254 nm in MeOH, reasonably via the nitrophenyl localized triplet.     

Coumarin phosphorescence observed with N^N Pt(II) bisacetylide complex and its applications for luminescent oxygen sensing and triplet-triplet-annihilation based upconversion

A dbbpy platinum(II) bis(coumarin acetylide) complex (Pt-1, dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine) was prepared. Pt-1 shows intense absorption in the visible region (λ(abs) = 412 nm, ε = 3.23 × 10(4) M(-1) cm(-1)) compared to the model complex dbbpy Pt(II) bis(phenylacetylide) (Pt-2, λ(abs) = 424 nm, ε = 8.8 × 10(3) M(-1) cm(-1)). Room temperature phosphorescence was observed for Pt-1 ((3)IL, τ(P) = 2.52 μs, λ(em) = 624 nm, Φ(P) = 2.6%) and the emissive triplet excited state was assigned as mainly intraligand triplet excited state ((3)IL), proved by 77 K steady state emission, nanosecond time-resolved transient absorption spectroscopy and DFT calculations. Complex Pt-1 was used for phosphorescent oxygen sensing and the sensitivity (Stern-Volmer quenching constant K(SV) = 0.012 Torr(-1)) is 12-fold of the model complex Pt-2 (K(SV) = 0.001 Torr(-1)). Pt-1 was also used as triplet sensitizer for triplet-triplet-annihilation based upconversion, upconversion quantum yield Φ(UC) up to 14.1% was observed, vs. 8.9% for the model complex Pt-2.     

Long-lived and temperature-independent emission from a novel ruthenium(II) complex having an arylborane charge-transfer unit

We report the redox, absorption, and emission characteristics of the tris(1,10-phenanthroline)ruthenium(II) complexes [Ru(phen)(3)](2+) bearing a (dimesityl)boryldurylethynyl (DBDE) charge-transfer (CT) unit at the 4 (4BRu(2+)) or 5 (5BRu(2+)) position of one of the three phen ligands. In acetonitrile at 298 K, 4BRu(2+) showed absorption and emission maximum wavelengths at 473 and 681 nm, respectively, which were shifted to longer wavelengths by 25 and 74 nm, respectively, compared with the relevant value of 5BRu(2+), 448 and 607 nm, respectively. The effects of a fluoride ion on the absorption and emission spectra of the complexes demonstrated that the CT interaction between the π-electron system in the phen ligand (π(aryl)) and the vacant p orbital on the boron atom (p(B)) in the DBDE group (i.e., π(aryl)-p(B) CT) participated in the excited states of the complexes in addition to the Ru(II)-to-phen metal-to-ligand CT (MLCT) interaction. Reflecting such synergistic MLCT/π(aryl)-p(B) CT, both 4BRu(2+) and 5BRu(2+) exhibited intense emission at 298 K with a quantum yield of 0.11. Furthermore, the emission lifetime of 4BRu(2+) was as long as 12 μs and almost independent of the temperature (T = 280-330 K). The present study indicated that the nonemissive dd excited triplet state did not participate to nonradiative decay in the MLCT excited triplet state of 4BRu(2+). The effects of the synergistic MLCT/π(aryl)-p(B) CT interactions on the redox, absorption/emission, and photophysical characteristics of 4BRu(2+) and 5BRu(2+) are discussed in detail.     

Singlet and triplet potential surfaces for the O2+C2H4 reaction

Electronic structure calculations at the CASSCF and UB3LYP levels of theory with the aug-cc-pVDZ basis set were used to characterize structures, vibrational frequencies, and energies for stationary points on the ground state triplet and singlet O(2)+C(2)H(4) potential energy surfaces (PESs). Spin-orbit couplings between the PESs were calculated using state averaged CASSCF wave functions. More accurate energies were obtained for the CASSCF structures with the MRMP2/aug-cc-pVDZ method. An important and necessary aspect of the calculations was the need to use different CASSCF active spaces for the different reaction paths on the investigated PESs. The CASSCF calculations focused on O(2)+C(2)H(4) addition to form the C(2)H(4)O(2) biradical on the triplet and singlet surfaces, and isomerization reaction paths ensuing from this biradical. The triplet and singlet C(2)H(4)O(2) biradicals are very similar in structure, primarily differing in their C-C-O-O dihedral angles. The MRMP2 values for the O(2)+C(2)H(4)→C(2)H(4)O(2) barrier to form the biradical are 33.8 and 6.1 kcal/mol, respectively, for the triplet and singlet surfaces. On the singlet surface, C(2)H(4)O(2) isomerizes to dioxetane and ethane-peroxide with MRMP2 barriers of 7.8 and 21.3 kcal/mol. A more exhaustive search of reaction paths was made for the singlet surface using the UB3LYP/aug-cc-pVDZ theory. The triplet and singlet surfaces cross between the structures for the O(2)+C(2)H(4) addition transition states and the biradical intermediates. Trapping in the triplet biradical intermediate, following (3)O(2)+C(2)H(4) addition, is expected to enhance triplet→singlet intersystem crossing.     

A theoretical study of the mechanism and kinetics of F+N3 reactions.

Both the singlet(1A') and triplet(3A') potential energy surfaces (PESs) of F+N(3) reactions are investigated using the complete-active-space self-consistent field (CASSCF) and the multireference configuration interaction (MRCI) methods with a proper active space. The minimum energy crossing point (MECP) at the intersection seam between the 1A' and 3A' PESs is located and used to clarify the reaction mechanisms. Two triplet transition states are found, with one in the cis form and the other one in the trans form. Further kinetic calculations are performed with the canonical unified statistical (CUS) theory on the singlet PES and the improved canonical variational transition-state (ICVT) method on the triplet PES. The rate constants are also reported. At 298 K, the calculated rate constant is in reasonably good agreement with experimental values, and spin-orbit coupling effects lower it by 28 %. The spectroscopic constants derived from the fitted potential-energy curves for the singlet and triplet states of NF are in very good agreement with experimental values. Our calculations indicate that the adiabatic reaction on the singlet PES leading to NF(a(1)Delta)+N(2) is the major channel, whereas the nonadiabatic reaction through the MECP, which leads to NF(X(3)Sigma(-))+N(2), is a minor channel.     

Direct observation of the luminescence from the (3)deltadelta excited state of Re(2)Cl(2)(p-OCH(3)form)(4)

There are only a few reports on the measurement of the energy of the low-lying (3)deltadelta state of quadruply bonded bimetallic complexes, and the direct observation of the (1)deltadelta excited electronic state was only recently reported. In the quadruply bonded bimetallic complexes reported to date, luminescence arises from their (1)deltadelta excited state, and the (3)deltadelta state is nonemissive. Here we report the luminescence of Re(2)Cl(2)(p-OCH(3)form)(4) [p-OCH(3)form = (p-CH(3)OC(6)H(4))NCHN(p-CH(3)OC(6)H(4))(-)] observed upon 400-460 nm excitation with maxima at 820 nm (CH(2)Cl(2), tau = 1.4 micros) and 825 nm (CH(3)CN, tau = 1.3 micros) at 298 K. From the large Stokes shift, the vibronic progression at 77 K, the quenching by O(2), the long lifetime, and the calculated energy of the (3)deltadelta state, the luminescence of Re(2)Cl(2)(p-OCH(3)form)(4) and the corresponding transient absorption signal are assigned as arising from the (3)deltadelta ((3)A(2u)) excited state of the complex.     

Triplet energy transfers in electrostatic host-guest assemblies of unsaturated organometallic cluster cations and carboxylate-containing porphyrin pigments

The unsaturated cyclic [M3(dppm)3(CO)](2+) clusters (M = Pt, Pd; dppm = Ph2PCH2PPh2; such as PF6(-) salt) exhibit a cavity formed by the six dppm-phenyl groups placed like a picket fence above the unsaturated triangular M3 dicationic center. Electrostatic interactions of the M(3+) units inside this cavity with the carboxylate anion RCO2(-) [R = tetraphenylporphyrinatozinc(II), ZnTPP; p-phenyltritolylporphyrinatozinc(II), ZnTTPP; p-phenyltritolylporphyrinatopalladium(II), PdTTPP] form dyads for through-space triplet energy transfers. The binding constants are on the order of 20,000 M(-1) in all six cases (298 K). The energy diagram built upon absorption and emission spectra at 298 and 77 K places the [Pt3(dppm)3(CO)](2+) and [Pd3(dppm)3(CO)](2+) as triplet energy donors, respectively, with respect to the ZnTPPCO2(-), ZnTTPPCO2(-), and PdTTPPCO2(-) pigments, which act as acceptors. Evidence for energy transfer is provided by the transient absorption spectra at 298 K, where triplet-triplet absorption bands of the metalloporphyrin chromophores are depicted at all time (at 298 K) with total absence of the charge-separated state in the nanosecond to microsecond time scale. Rates for energy transfer (ranging in the 10(4) s(-1) time scale) are extracted from the emission lifetimes of the [Pt3(dppm)3(CO)](2+) donor in the free chromophore and the host-guest assemblies. The emission intensity of [Pd3(dppm)3(CO)](2+) is too weak to measure its spectrum and emission lifetime in the presence of the strongly luminescent metalloporphyrin-containing materials. For the [Pd3(dppm)3(CO)](2+)...metalloporphyrin dyads, evidence for fluorescence and phosphorescence lifetime quenching of the porphyrin chromophore at 298 K is provided. These quenchings, exhibiting rates of 10(4) (triplet) and 10(8) s(-1) (singlet), are attributed to a photoinduced electron transfer from the metalloporphyrin to the cluster due to the low reduction potential.     

Photolysis of (3-methyl-2H-azirin-2-yl)-phenylmethanone: direct detection of a triplet vinylnitrene intermediate

The photoreactivity of (3-methyl-2H-azirin-2-yl)-phenylmethanone, 1, is wavelength-dependent (Singh et al. J. Am. Chem. Soc. 1972, 94, 1199-1206). Irradiation at short wavelengths yields 2P, whereas longer wavelengths produce 3P. Laser flash photolysis of 1 in acetonitrile using a 355 nm laser forms its triplet ketone (T(1K), broad absorption with λ(max) ~ 390-410 nm, τ ~ 90 ns), which cleaves and yields triplet vinylnitrene 3 (broad absorption with λ(max) ~ 380-400 nm, τ = 2 μs). Calculations (B3LYP/6-31+G(d)) reveal that T(1K) of 1 is located 67 kcal/mol above its ground state (S(0)) and has a long C-N bond (1.58 ?), and the calculated transition state to form 3 is only 1 kcal/mol higher in energy than T(1K) of 1. The calculations show that 3 has significant 1,3-carbon iminyl biradical character, which explains why 3 reacts efficiently with oxygen and decays by intersystem crossing to the singlet surface. Photolysis of 1 in argon matrixes at 14 K produced ketene imine 7, which presumably is formed from 3 intersystem crossing to 7. In comparison, photolysis of 1 in methanol with a 266 nm laser produces mainly ylide 2 (λ(max) ~ 380 nm, τ ~ 6 μs, acetonitrile), which decays to form 2P. Ylide 2 is formed via singlet reactivity of 1, and calculations show that the first singlet excited state of the azirine chromophore (S(1A)) is located 113 kcal/mol above its S(0) and that the singlet excited state of the ketone (S(1K)) is 85 kcal/mol. Furthermore, the transition state for cleaving the C-C bond in 1 to form 2 is located 49 kcal/mol above the S(0) of 1. Thus, we theorize that internal conversion of S(1A) to a vibrationally hot S(0) of 1 forms 2, whereas intersystem crossing from S(1K) to T(1K) results in 3.     

微波辐射法合成喹喔啉铱（Ⅲ）配合物及其发光性质

采用微波辐射加热方法,将2,3-二苯基喹喔啉（DPQ）与水合三氯化铱（IrCl3•H2O）反应,合成了一种新型三环喹喔啉铱配合物[Ir(DPQ)3],通过元素分析,1H NMR和质谱方法对配合物结构进行了表征,并初步研究了配合物的吸收光谱和荧光光谱。结果表明,配合物Ir(DPQ)3在387和458nm处存在单线态1MLCT（金属到配体的电荷跃迁）和三线态3MLCT的吸收;在634nm 处有较强的金属配合物三线态的磷光发射。     

Intramolecular singlet and triplet excimers of triply bridged [3.3.N](3,6,9)carbazolophanes

Intermoiety electronic interactions in the singlet and triplet excimer states of triply bridged [3.3.n](3,6,9)carbazolophanes ([3.3.n]Cz, n=3-6) were studied by emission and transient absorption measurements. In these [3.3.n]Cz molecules, the dihedral angle and the separation distance r between fully overlapped two carbazole rings change systematically from nearly parallel (n=3, r=3.35 A) to oblique (n=6, r=4.03 A). In rigid glass at 77 K, [3.3.n]Cz (n=3, 4) (r<4 A) exhibited red-shifted and structureless excimer fluorescence and phosphorescence while [3.3.n]Cz (n=5, 6) (r>4 A) exhibited monomer-like vibrational fluorescence and phosphorescence. In solution at 130 K, all [3.3.n]Cz molecules exhibited an excimeric fluorescence band while [3.3.5]Cz still exhibited monomer-like phosphorescence. Transient absorption spectra measured at 294 K exhibited local excitation and charge-transfer bands for all [3.3.n]Cz molecules in the excited singlet and triplet states, suggesting that not only singlet but also triplet excimers of carbazole are formed at room temperature. Furthermore, the singlet-triplet energy gap decreased with the decrease in n, suggesting that electrons are effectively delocalized over the two carbazole moieties. These findings showed that both singlet and triplet excimers of carbazole are formed with a separation distance shorter than about 4 A and are most stable in the parallel-sandwich structure and that the configurational mixing between exciton resonance and charge resonance states plays an essential role in the formation of singlet and triplet excimers of carbazole.     

Multiple charge-transfer emissions from different metal-ligand pairs in ruthenium diimines

Ruthenium diimines are unique in their emissivity. Optical excitation with light of less than 500 nm leads to a strong emission in the 600-700 nm range. All emissive ruthenium complexes appear to undergo intersystem crossing from the absorptive singlet metal-to-ligand charge-transfer (MLCT) state to an emissive triplet MLCT state localized on the lowest-energy metal-ligand pair. In contrast to this currently accepted model, in which a single emissive state is populated and then equilibrates among other states based on a particular set of conditions, the excitation-wavelength dependence of the [(bpy)2RudppH]3+ emission suggests two emissive pathways. One populates an emissive MLCT state localized on a bpy-Ru pair, and the other populates a lower-energy MLCT state localized on the dpp-Ru pair.     

Water affects the stereochemistry and dioxygen reactivity of carboxylate-rich diiron(II) models for the diiron centers in dioxygen-dependent non-heme enzymes

Carboxylate-bridged high-spin diiron(II) complexes with distinctive electronic transitions were prepared by using 4-cyanopyridine (4-NCC(5)H(4)N) ligands to shift the charge-transfer bands to the visible region of the absorption spectrum. This property facilitated quantitation of water-dependent equilibria in the carboxylate-rich diiron(II) complex, [Fe(2)(mu-O(2)CAr(Tol))(4)(4-NCC(5)H(4)N)(2)] (1), where (-)O(2)CAr(Tol) is 2,6-di-(p-tolyl)benzoate. Addition of water to 1 reversibly shifts two of the bridging carboxylate ligands to chelating terminal coordination positions, converting the structure from a paddlewheel to a windmill geometry and generating [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(4-NCC(5)H(4)N)(2)(H(2)O)(2)] (3). This process is temperature dependent in solution, rendering the system thermochromic. Quantitative treatment of the temperature-dependent spectroscopic changes over the temperature range from 188 to 298 K in CH(2)Cl(2) afforded thermodynamic parameters for the interconversion of 1 and 3. Stopped flow kinetic studies revealed that water reacts with the diiron(II) center ca. 1000 time faster than dioxygen and that the water-containing diiron(II) complex reacts with dioxygen ca. 10 times faster than anhydrous analogue 1. Addition of {H(OEt(2))(2)}{B}, where B(-) is tetrakis(3,5-di(trifluoromethyl)phenyl)borate, to 1 converts it to [Fe(2)(mu-O(2)CAr(Tol))(3)(4-NCC(5)H(4)N)(2)](B) (5), which was also structurally characterized. Mossbauer spectroscopic investigations of solid samples of 1, 3, and 5, in conjunction with several literature values for high-spin iron(II) complexes in an oxygen-rich coordination environment, establish a correlation between isomer shift, coordination number, and N/O composition. The products of oxygenating 1 in CH(2)Cl(2) were identified crystallographically to be [Fe(2)(mu-OH)(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(4-NCC(5)H(4)N)(2)].2(HO(2)CAr(Tol)) (6) and [Fe(6)(mu-O)(2)(mu-OH)(4)(mu-O(2)CAr(Tol))(6)(4-NCC(5)H(4)N)(4)Cl(2)] (7).     

新型铱(Ⅲ)配合物有机磷光材料的合成及性能研究

以苯甲酰氯及其衍生物、邻氨基苯硫酚等为原料, 通过与无水三氯化铱及乙酰丙酮配合, 合成了一系列新型的取代2-苯基苯并噻唑合铱(Ⅲ)的乙酰丙酮类配合物有机磷光材料, 并对产物进行了核磁、红外、质谱和元素分析等结构表征及溶解性能、热稳定性和紫外吸收光谱、荧光光谱等发光性能的研究. 结果表明, 此类配合物在二甲亚砜和三氯甲烷等有机溶剂中具有良好的溶解性; 配合物分解温度高, 可达338～360 ℃, 具有较高的热稳定性, 其高温升华现象十分有利于真空热蒸镀薄膜的制备; 此类配合物在紫外-可见吸收光谱上的250～350 nm处出现了强的配体自旋, 允许单重态π-π*跃迁吸收峰, 在400～530 nm处出现了配合物分子内金属铱到配体的单重态和三重态电荷跃迁吸收峰(1MLCT和3MLCT); 同时, 该类铱(Ⅲ)配合物在发射光谱560～600 nm处出现了强的黄光发射, 并且在室温下表现出较高的荧光量子效率.     

Spectroscopic characterization of chloride and pseudohalide ruthenium(II) complexes with 4-(4-nitrobenzyl)pyridine

Chloride, isocyanate and isothiocyanate hydride carbonyl ruthenium(II) complexes of 4-(4-nitrobenzyl)pyridine were synthesized from the precursor complex [RuHCl(CO)(PPh₃)₃] and characterized by IR, NMR, UV–Vis spectroscopy and X-ray crystallography. The electronic structures of the complexes were investigated by means of DFT calculations, based on their crystal structures. The spin-allowed singlet–singlet electronic transitions of the complexes were calculated by time-dependent DFT, and the UV–Vis spectra are discussed on this basis. The emission properties of the complexes were studied at ambient temperature, and the quantum yields of fluorescence, the lifetimes and nature of the excited states are discussed. The chloride and isothiocyanate complexes are practically nonemissive, with quantum yields under 0.01 %. Interpretation of spectra, supported by TD-DFT calculations, indicates that in this energy region, the transitions have MLCT character with admixture of LLCT (chloride and isothiocyanate complexes). The dominant LLCT character was visible in the case of the most emissive (isocyanate) complex. The low values of the lifetimes and quantum yields for these complexes indicate the influence of the metal center in the emission process.     

Cucurbit[8]uril-mediated phosphorescent supramolecular foldamer for antibiotics sensing in water and cells

A phosphorescent supramolecular foldamer is conveniently constructed by the 1:1 host–guest complexation with cucurbit[8]uril and 1,2-diaminocyclohexane-bridged 4-(4-bromophenyl)-pyridinium salt. The tightly compact host–guest complexation in molecular foldamer can greatly suppress the fluorescence emissive channel and promote the intersystem crossing from singlet to triplet states, thus leading to the green phosphorescence at ambient temperature in aqueous solution. More intriguingly, the phosphorescence emission shows very rapid and sensitive responsiveness to different antibiotics in both inanimate milieu and living cells. Remarkably, the limit of detection of such binary inclusion complex toward sulfamethazine can reach as low as 1.86 × 10^?7 mol/L. Thus, it is envisaged that this supramolecular nanoplatform featuring unique complexation-enhanced phosphorescence emission may hold great promise in sensing and detecting many other biological targets under physiological environment.     

Photophysical properties of highly luminescent copper(I) halide complexes chelated with 1,2-bis(diphenylphosphino)benzene

Studies on synthesis, structures, and photophysics have been carried out for a series of luminescent copper(I) halide complexes with the chelating ligand, 1,2-bis[diphenylphosphino]benzene (dppb). The complexes studied are halogen-bridged dinuclear complexes, [Cu(mu-X)dppb]2 (X = I (1), Br (2), Cl (3)), and a mononuclear complex, CuI(dppb)(PPh3) (4). These complexes in the solid state exhibit intense blue-green photoluminescence with microsecond lifetimes (emission peaks, lambdamax = 492-533 nm; quantum yields, Phi = 0.6-0.8; and lifetimes, tau = 4.0-10.4 mus) at 298 K. In 2-methyltetrahydrofuran (2mTHF) solutions at 298 K, only 1 and 4 show weaker emission (Phi = 0.009) with shorter lifetimes (tau = 0.35 and 0.23 mus) and red-shifted spectra (lambdamax = 543 and 546 nm). The emission in the solid state originates from the (M + X)LCT excited state with a distorted-tetrahedral conformation, in which emissive excited states, 1(M + X)LCT and 3(M + X)LCT, are in equilibrium with an energy difference of approximately 2 kcal/mol. On the other hand, the complexes in the 2mTHF solutions emit from the MLCT excited state with an energetically favorable flattened conformation in the temperature range of 298-130 K. The flattened geometry with equilibrated 1MLCT and 3MLCT states has a nonradiative rate at least 2 orders of magnitude larger than that of the distorted-tetrahedral geometry, leading to a much smaller emission quantum yield (Phi = 0.009) at 298 K. Since the flattening motion is markedly suppressed below 130 K, the emission observed in 2mTHF below 130 K is considered to occur principally from the (M + X)LCT state with a distorted-tetrahedral geometry. To interpret the photophysics of 1 and 4 in both the solid and solution states, we have proposed the "2-conformations with 2-spin-states model (2C x 2S model)". The electroluminescence device using (1) as a green emissive dopant showed a moderate EL efficiency; luminous efficiency = 10.4 cd/A, power efficiency = 4.2 lm/W at 93 cd/m(2), and maximum external quantum efficiency = 4.8%.