A heteronuclear bidentate Lewis acid as a phosphorescent fluoride sensor

Reaction of dimesityl-1,8-naphthalenediylborate (1) with C6F5HgCl results in the formation of a B/Hg heteronuclear bidentate Lewis acid (2), which complexes fluoride to afford [2-mu2-F]-. Structural and photophysical studies carried out in solution and in the solid state indicate that 2 is a highly selective and sensitive phosphorescent fluoride sensor. The proximity of the two Lewis acidic sites enforced by the 1,8-naphthalenediyl backbone promotes fluoride anion chelation and is, therefore, responsible for the high binding constant. The interplay of conjugative and spin-orbit coupling effects mediated by the boron and mercury atoms, respectively, results in the phosphorescent signaling of fluoride binding. Remarkably, fluoride binding occurs in partially aqueous solutions and results in a drastic change of the phosphorescence observed when the solutions are frozen.     

Metal effect on the supramolecular structure, photophysics, and acid-base character of trinuclear pyrazolato coinage metal complexes

Varying the coinage metal in cyclic trinuclear pyrazolate complexes is found to significantly affect the solid-state packing, photophysics, and acid-base properties. The three isoleptic compounds used in this study are [[3,5-(CF3)2Pz]M]3 with M = Cu, Ag, and Au (i.e., Cu3, Ag3, and Au3, respectively). They form isomorphous crystals and exist as trimers featuring nine-membered M3N6 rings with linear two-coordinate metal sites. On the basis of the M-N distances, the covalent radii of two-coordinate Cu(I), Ag(I), and Au(I) were estimated as 1.11, 1.34, and 1.25 angstroms, respectively. The cyclic [[3,5-(CF3)2Pz]M]3 complexes pack as infinite chains of trimers with a greater number of pairwise intertrimer M...M interactions upon proceeding to heavier coinage metals. However, the intertrimer distances are conspicuously short in Ag3 (3.204 angstroms) versus Au3 (3.885 angstroms) or Cu3 (3.813 angstroms) despite the significantly larger covalent radius of Ag(I). Remarkable luminescence properties are found for the three M3 complexes, as manifested by the appearance of multiple unstructured phosphorescence bands whose colors and lifetimes change qualitatively upon varying the coinage metal and temperature. The multiple emissions are assigned to different phosphorescent excimeric states that exhibit enhanced M...M bonding relative to the ground state. The startling luminescence thermochromic changes in crystals of each compound are related to relaxation between the different phosphorescent excimers. The trend in the lowest energy phosphorescence band follows the relative triplet energy of the three M(I) atomic ions. DFT calculations indicate that [[3,5-(R)2Pz]M]3 trimers with R = H or Me are bases with the relative basicity order Ag < Cu < Au while fluorination (R = CF3) renders even the Au trimer acidic. These predictions were substantiated experimentally by the isolation of the first acid-base adduct, [[Au3]2:toluene]infinity, in which a trinuclear Au(I) complex acts as an acid.     

A phosphorescent copper(I) complex: synthesis, characterization, photophysical property, and oxygen-sensing behavior

In this paper, we report the synthesis, crystal structure, photophysical properties, and electronic nature of a phosphorescent Cu(I) complex of [Cu(Phen-Np)(POP)]BF4, where Phen-Np and POP stand for 2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline and bis(2-(diphenylphosphanyl)phenyl) ether, respectively. [Cu(Phen-Np)(POP)]BF4 renders a yellow phosphorescence peaking at 545 nm, with a long excited state lifetime of 4.69 μs. Density functional calculation reveals that the emission comes from a triplet metal-to-ligand-charge-transfer excited state. We electrospun composite nanofibers of [Cu(Phen-Np)(POP)]BF4 and polystyrene (PS), hoping to explore the possibility of using the composite nanofibers as an oxygen sensing material. The finally obtained samples with average diameter of ～300 nm exhibit a maximum sensitivity of 7.2 towards molecular oxygen with short response time of 7s due to the large surface-area-to-volume ratio of nanofibrous membranes. No photobleaching is detected in these samples.     

Synthesis,characterization, photophysical and oxygen-sensing properties of a copper(I) complex

In this paper, we report the synthesis, crystal structure, photophysical properties, and electronic nature of a phosphorescent Cu(I) complex of [Cu(TBT)(POP)]BF₄, where TBT and POP stand for 4,5,9,14-tetraaza-benzo[b]triphenylene and bis(2-(diphenylphosphanyl)phenyl) ether, respectively. [Cu(TBT)(POP)]BF₄ renders a red phosphorescence peaking at 622 nm, with a long excited-state lifetime of 13.2 μs. Density functional calculation reveals that the emission comes from a triplet metal-to-ligand-charge-transfer excited state. We electrospun composite nanofibers of [Cu(TBT)(POP)]BF₄ and polystyrene, hoping to explore the possibility of replacing precious-metal-based oxygen sensors with cheap Cu-based ones. The finally obtained samples with average diameter of ~700 nm exhibit a maximum sensitivity of 5.8 toward molecular oxygen with short response/recovery time (5/13 s) due to the large surface-area-to-volume ratio of nanofibrous membranes. No photobleaching is detected in these samples. All these results suggest that phosphorescent Cu(I) complexes doped nanofibrous membranes are promising candidates for low-cost and quick-response oxygen-sensing materials.     

Effects of intramolecular hydrogen bonds on phosphorescence emission: A theoretical perspective

Importing intramolecular hydrogen bond in phosphorescent transition metal complexes has been considered one of the excellent approaches to improve the electroluminescence performance of organic light-emitting diodes in real applications. However, the relationships between such H-bond structure and phosphorescent properties have not been theoretically revealed yet. In this study, two types of intramolecular hydrogen bonds are introduced into the two classes of traditional materials, that is, Pt(II) and Ir(III) complexes ( 1a and 2a ) to completely elucidate their influence on the structures and properties by comparing with the original phosphors ( 1b and 2b ) using density functional theory/time-dependent density functional theory for the first time. A comprehensive analysis of the geometric structures, molecular orbitals, and luminescence properties (including phosphorescence emission wavelengths and radiative and nonradiative decay processes) has been carried out. Our theoretical model highlights that complexes 1a and 2a embedded with H-bonds significantly promote the phosphorescence emission band blue-shifted and restrict molecular deformations compared with the corresponding 1b and 2b , which can provide helpful guidance to regulate and design several aspects of highly efficient blue phosphorescent emitters.     

Ratiometric phosphorescence imaging of Hg(II) in living cells based on a neutral iridium(III) complex

In this work, a neutral iridium(III) complex [Ir(bt)(2)(acac)] (Hbt = 2-phenylbenzothiazole; Hacac = acetylacetone) has been realized as a Hg(II)-selective sensor through UV-vis absorption, phosphorescence emission, and electrochemical measurements and was further developed as a phosphorescent agent for monitoring intracellular Hg(II). Upon addition of Hg(II) to a solution of [Ir(bt)(2)(acac)], a noticeable spectral blue shift in both absorption and phosphorescent emission bands was measured. (1)H NMR spectroscopic titration experiments indicated that coordination of Hg(II) to the complex induces fast decomposition of [Ir(bt)(2)(acac)] to form a new complex, which is responsible for the significant variations in optical and electrochemical signals. Importantly, cell imaging experiments have shown that [Ir(bt)(2)(acac)] is membrane permeable and can be used to monitor the changes in Hg(II) levels within cells in a ratiometric phosphorescence mode.     

Room-temperature liquid phosphorimetry of the aluminium-ferron chelate in micellar media : Determination of aluminium

Aluminium reacts with 7-iodo-8-quinolinol-5-sulphonic acid (Ferron) in cetyltrimethylammonium bromide (CTAB) micelles to form a highly phosphorescent complex at room temperature. Suitable experimental conditions and the phosphorescent characteristics of the complex are described. Comparison with the results obtained for the phosphorescent niobium-Ferron complex in CTAB micelles helps to elucidate the mechanism of this type of phosphorescence. For aluminium the detection limit is 5.4 ng ml^?1; the relative standard deviation is 4.5% for 20 μg Al. The method is applied to aluminium determination in waters and dialysis fluids.     

Study on the kinetic properties of phosphor in deoxycholate aggregates by phosphorescent quenching methodology

Owing to the unique molecular structure and aggregate behaviors in aqueous solution, dihydroxy bile salts can provide phosphorescent probe with a special microenvironment in which the room temperature phosphorescence of probe can be detected in the presence of dissolved oxygen. It, however, is not very clear how the bile salts work in inducing this kind of oxygen-independent phosphorescence. The present work tries to offer with possible more insights by investigating the particular kinetic behaviors of 3-bromoquinoline (3-BrQ) as probe in sodium deoxycholate (NaDC) aggregate based on phosphorescent quenching methodology. The critical aggregate concentration of NaDC is estimated as about 0.5mM based on the enhancement of probe phosphorescence. As the functions of quencher Cu(2+) and NO(2)(-), the rate constants of various photophysical processes for 3-BrQ are obtained in NaDC solution and full aqueous solution, respectively. In NaDC solution, the quenching rate constant k(cu2+) equals to 1.77x10(7)M(-1)s(-1) k(no-2)(mq) 1.62x10(6)M(-1)s(-1). The exit rate k(-) and entrance rate k(+) are determined to be 16-46s(-1) and 10(6)M(-1)s(-1) levels, respectively. The quenching rate constant k(o2)(q) of dissolved oxygen is estimated as 4.15x10(4)M(-1)s(-1) in air-saturated NaDC solution at 1atm.     

沸石型咪唑锌框架MAF-6的一价铜磷光掺杂

基于Cu(I)的配合物具有成本便宜和发光寿命长等有利于荧光传感的独到优势。但是,大部分Cu(Ⅰ)配合物在空气中不稳定,易被氧气氧化,或者比较难形成多孔框架。在沸石型咪唑锌多孔配位聚合物中,RHO-[Zn(eim)_2](MAF-6,Heim=2-ethylimidazole)由于其较大的孔径和优异的疏水特性而备受关注。本文利用Cu(I)离子与Zn(Ⅱ)离子相似的配位习性,用Cu(I)离子部分取代MAF-6中的Zn(II)离子,得到同构的磷光多孔配位聚合物Cu:MAF-6。该材料在极低氧气压力环境(600 Pa)中表现出非常灵敏的氧气荧光传感性能(Ksv=28.09 k Pa~(-1);检测限0.36 Pa)。     

Effects of the Au(I)–Au(I) closed‐shell attraction on the electronic and phosphorescent properties in a series of coordination compounds: A theoretical study

The Au(I)–Au(I) closed‐shell or aurophilic attraction has been the subject of interest in the experimental and theoretical chemistry fields, due to the intriguing properties associated to it. The presence of phosphorescence in “aurophilic” compounds has been addressed to a wide range of applications, but it has not yet been fully understood. A theoretical study on the electronic and phosphorescent properties of the following series of dinuclear gold complexes has been performed: [Au₂(dmpm) (i‐mnt)] ( 1 ), [Au₂(μ‐Me‐TU) (μ‐dppm)] ( 2 ), and [Au₂(μ‐G)(μ‐dmpe)] ( 3 ). Full geometry optimizations at the second‐order Møller–Plesset perturbation theory (MP2) were carried out for each of the species. These calculations made evident that, at the ground‐state geometry, the Au(I) cations allocated at the center of the ring show a short Au–Au distance below the sum of the van der Waals radii, at the range of the aurophilic attraction. An intermolecular Au(I)–Au(I) closed‐shell attraction for a pair of the systems under study is found. This attraction is comparable to that of the hydrogen bonds. The phosphorescent properties experimentally observed for this series were also characterized through ab initio techniques. The obtained results allow to fit reasonably the excitation energies with the experimental data and to identify a correlation between the strength of the Au(I)–Au(I) interaction and the phosphorescent behavior. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

The development of an iridium(III) complex functionalized G-quadruplex probe for the stability of G-quadruplex and lifetime image in cytoplasm

G-quadruplex (G4) is widely known as a non-classical secondary structure of nucleic acid. With the in-depth study of G4, it is an urgent need for a phosphorescent probe with a high G4 binding ability to evaluate the level of G4 in the cytoplasm. Thus, this study designed and synthesized Ir-PDP where an Ir(III) complex was used as a phosphorescent emitter. Meanwhile, two installed PDPs (pyridostatin derivatives) were used to improve the combination ability with G4 and reduced the cytotoxicity of the Ir(III) complex. Compared with other nucleic acid secondary structures, Ir-PDP produced a higher phosphorescence lifetime after interacting with G4. Ir-PDP was distributed in the cytoplasm of living cells, and two-photon phosphorescence lifetime imaging can detect the binding events of the probe in the cytoplasm. The addition of G4 binder PDS significantly regulated cytoplasmic phosphorescence lifetime. The project explored a new sensing pathway to observe the binding manners of probes in the cytoplasm through the phosphorescence lifetime of probes.     

8‐Hydroxy Quinoline Derivatives as Auxiliary Ligands for Red‐Emitting Cyclic‐Platinum Phosphorescent Complexes: Synthesis and Properties

Heavy metal complexes exhibit high phosphorescent efficiency and have been used extensively for electrophosphorescent emitters in the past 16 years. In 2006, we initially reported the use of the popular ligand, 8‐hydroxyquinoline (Q) to coordinate with the heavy metal ions and obtained the red‐infrared phosphorescent emission. In this paper, 8‐hydroxyquinoline has been modified at the 5‐position by electron‐donating and attracting groups and platinum complexes based on 2‐phenylpyridine and 8‐hydroxyquinoline derivatives were synthesized. The electron‐withdrawing group CF ₃ and NO ₂ lowers the HOMO level of the Q ligand and results in a N^O centered enhanced red‐infrared phosphorescence emission. The complex with CF ₃ modification exhibits the highest phosphorescence quantum yield in solid state with a life time of 1.17 μs.     

Multifunctional red phosphorescent bis-cyclometallated iridium complexes based on 2-phenyl-1,2,3-benzotriazole ligand and carbazolyl moieties

Multifunctional phosphorescent bis-cyclometallated iridium(III) complexes based on the 2-phenyl-1,2,3-benzotriazole moiety and bearing branched hole-transporting carbazole fragments were synthesized. The isolated compounds were found to be amorphous and expressed very good solubility. Introduction of flexible aliphatic chains of various lengths into the iridium complexes enabled manipulation of their glass transition temperature. The iridium complexes exhibited red phosphorescence emission at 650 nm with the lifetime of 5.7 μs and phosphorescence quantum yields of 0.22 and 0.17 in solution and solid state, respectively, at room temperature. The shielding effect of the carbazolyl moieties on the concentration quenching of phosphorescence of the iridium centers was found to result in the increased excited state lifetime and quantum yield due to the suppressed exciton migration. Non-optimized OLED devices, based on the phosphorescent bis-cyclometallated iridium(III) complex without host material were fabricated and their electroluminescence properties were evaluated.     

Phosphorescent sensor for robust quantification of copper(II) ion

A phosphorescent sensor based on a multichromophoric iridium(III) complex was synthesized and characterized. The construct exhibits concomitant changes in its phosphorescence intensity ratio and phosphorescence lifetime in response to copper(II) ion. The sensor, which is reversible and selective, is able to quantify copper(II) ions in aqueous media, and it detects intracellular copper ratiometrically.     

一种新型吡嗪铱（Ⅲ）配合物的合成及其磷光性质

利用5-甲基-2,3-二苯基吡嗪（MDPP）和水合三氯化铱（IrCl3•H2O）,合成了一种新型吡嗪铱配合物Ir (MDPP)2 (acac).通过1H NMR、元素分析和质谱方法对配合物结构进行了表征,并研究了配合物的吸收光谱和光致发光光谱.结果表明,配合物Ir (MDPP)2(acac)在393和528 nm处存在单重态1MLCT（金属到配体的电荷跃迁）和三重态3MLCT的吸收;在588 nm 处有较强的金属配合物三重态的磷光发射,是一种绿色磷光材料.     

Rational Design of an “OFF–ON” Phosphorescent Chemodosimeter Based on an Iridium(III) Complex and Its Application for Time‐Resolved Luminescent Detection and Bioimaging of Cysteine and Homocysteine

Biothiols, such as cysteine (Cys) and homocysteine (Hcy), play very crucial roles in biological systems. Abnormal levels of these biothiols are often associated with many types of diseases. Therefore, the detection of Cys (or Hcy) is of great importance. In this work, we have synthesized an excellent “OFF‐ON” phosphorescent chemodosimeter 1 for sensing Cys and Hcy with high selectivity and naked‐eye detection based on an Ir^III complex containing a 2,4‐dinitrobenzenesulfonyl (DNBS) group within its ligand. The “OFF‐ON” phosphorescent response can be assigned to the electron‐transfer process from Ir^III center and C^N ligands to the DNBS group as the strong electron‐acceptor, which can quench the phosphorescence of probe 1 completely. The DNBS group can be cleaved by thiols of Cys or Hcy, and both the ³M LCT and ³LC states are responsible for the excited‐state properties of the reaction product of probe 1 and Cys (or Hcy). Thus, the phosphorescence is switched on. Based on these results, a general principle for designing “OFF‐ON” phosphorescent chemodosimeters based on heavy‐metal complexes has been provided. Importantly, utilizing the long emission‐lifetime of phosphorescence signal, the time‐resolved luminescent assay of 1 in sensing Cys was realized successfully, which can eliminate the interference from the short‐lived background fluorescence and improve the signal‐to‐noise ratio. As far as we know, this is the first report about the time‐resolved luminescent detection of biothiols. Finally, probe 1 has been used successfully for bioimaging the changes of Cys/Hcy concentration in living cells.     

Recent progress on pure organic room temperature phosphorescence materials based on host-guest interactions

Pure organic room temperature phosphorescence (RTP) has been attracting a lot interest recently. So far, many strategies have succeeded in achieving efficient organic RTP materials by increasing the rate of intersystem crossing (ISC) and suppressing non-radiative transitions. In supramolecular chemistry, the control and regulation of molecular recognition based on the role of the host and guest in supramolecular polymers matrix, has attracted much attention. Recently, researchers have successfully achieved room temperature phosphorescence of pure organic complexes through host-guest interactions. The host molecule specifically includes the phosphorescent guest to reduce non-radiative transitions and enhance room temperature phosphorescence emission. This review aims to describe the developments and achievements of pure organic room temperature phosphorescence systems through the mechanism of host-guest interactions in recent years, and demonstrates the exploration and pursuit of phosphorescent materials of researchers in different fields.     

Phosphorescent excited state of [Au2[(Ph2Sb)2O]3]2+: Jahn-Teller distortion at only one gold(I) center

Dinuclear three-coordinate Au(I) complex [Au2{(Ph2Sb)2O}3](ClO4)2 1 displays an interesting phosphorescent behavior in which a large Stokes' shift is observed. Ab initio calculations show that the main distortion for the first triplet excited state, which is responsible for the luminescence behavior of complex 1, is a Jahn-Teller distortion for only one of the Au(I) centers together with a gold-gold distance shortening. This behavior could be extrapolated to other phosphorescent dinuclear three-coordinate Au(I) complexes.     

Bright phosphorescence of a trinuclear copper(I) complex: luminescence thermochromism, solvatochromism, and "concentration luminochromism"

A photophysical study is reported for the trinuclear copper(I) complex {[3,5-(CF3)2Pz]Cu}3. The neutral compound exhibits multicolor bright phosphorescent emissions both in the solid state and in solution. The emission can be tuned to multiple visible colors by controlling the temperature, solvent, and {[3,5-(CF3)2Pz]Cu}3 concentration, giving rise to luminescence thermochromism, luminescence solvatochromism, and a new optical phenomenon called "concentration luminochromism", respectively.     

Recent progress on pure organic room temperature phosphorescence materials based on host-guest interactions

The inclusion of specific organic phosphorescent guest molecules by the host molecules can reduce the nonradiative transitions and engender room temperature phosphorescence emission.