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Significant advancements in perovskite light-emitting diodes (PeLEDs) based on ITO glass substrates have been realized in recent years, yet the overall performance of flexible devices still lags far behind, mainly being ascribed to the high surface roughness and poor optoelectronic properties of flexible electrodes. Here, we report efficient and robust flexible PeLEDs based on a mixed-dimensional (0D-1D-2D-3D) composite electrode consisting of 0D Ag nanoparticles (AgNPs)/1D Ag nanowires (AgNWs)/2D MXene/3D poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Our designed MXene-based electrodes combine the advantages of facile formation of a film of low-dimensional materials and excellent optical and electrical properties of metal, inorganic, and organic semiconductors, which endow the electrodes with high electrical/thermal conductivity, flexibility, a smooth surface, and good transmittance. Consequently, the resulting flexible PeLEDs (without a light-coupling structure) demonstrate a record external quantum efficiency of 16.5%, a high luminance of close to 50000 cd/m

A simple and efficient method for the silver-catalyzed regioselective phosphorylation of para-quinone methides (p-QMs) with P(III)-nucleophiles (P(OR)3, ArP(OR)2, Ar2P-OR) has been established via Michaelis-Arbuzov-type reaction. A broad range of P(III)-nucleophiles and para-quinone methides are well tolerated under the mild conditions, giving the expected diarylmethyl-substituted organophosphorus compounds with good to excellent yields. Moreover, a series of corresponding enantiomers can be obtained by employing dialkyl arylphosphonite (ArP(OR)2) as substrates. The control experiments and 31P NMR tracking experiments were also performed to gain insights for the plausible reaction mechanism. This protocol may have significant implications for the formation of C(sp3)-P bonds in Michaelis-Arbuzov-type reactions.

A new platinum(II) complex-based soft salt S1, ([Pt(tpp)(ed)]+[Pt(pba) (CN)2]-) (tpp = 2-(4-(trifluoromethyl)phenyl)pyridine, ed = ethane-1,2-diamine, pba = 4-(2-pyridyl)benzaldehyde), was designed and synthesized. UV-visible absorption and photoluminescence (PL) spectra were studied to elucidate the nature of ground and excited states. The soft salt complex was found to show self-assembly properties with the assistance of electrostatic, π-π stacking, and Pt···Pt interactions, resulting in the remarkable emergence of low-energy absorption and PL bands. Morphological transformation of S1 from undefined nanosized aggregates to nanofibers with different solvent compositions has been demonstrated. Interestingly, a luminescent polymer film was prepared by doping S1 into a polyethylene glycol matrix. The film displayed distinctive emission color change from yellow to red upon heating. Eventually, a high-level anti-counterfeiting application was accomplished using a time-resolved imaging technique based on the thermochromic luminescence property and long emission decay time displayed by S1. It is anticipated that this work can provide deep insights into the control of intermolecular interactions between cationic and anionic complexes of soft salt upon exposure to different external stimuli, resulting in the development of smart luminescent materials for various applications.

A simple heteroleptic iridium(III) photosensitizer, Ir-1, containing two ligands 5-(trifluoromethyl)-2-phenylpyridine (ĈN–CF3) and bipyridine (NN) has for the first time been studied for cocatalys...

Luminescent copper(I) halide complexes with bi- and tridentate rigid ligands have gained wide research interests. In this paper, six tetracoordinate dinuclear copper(I) halide complexes, Cu2X2(ppda)2 [ppda = 2-[2-(dimethylamino)phenyl(phenyl)phosphino]-N,N-dimethylaniline, X = I (1), Br (2), Cl (3)] and Cu2X2(pfda)2 [pfda = 2-[2-(dimethylamino)-4-(trifluoromethyl)phenyl(phenyl)phosphino]-N,N-dimethyl-5-trifluoromethylaniline, X = I (4), Br (5), Cl (6)], were successfully prepared and systematically characterized on their structures and photophysical properties. Complexes 1-5 have a centrosymmetric form with a planar Cu2X2 unit, and complex 6 has a mirror symmetry form with a butterfly-shaped Cu2X2. Solid complexes 1, 4, and 5 emit delayed fluorescence at room temperature, intense blue to greenish yellow (λmax = 443-570 nm) light, and their peak wavelengths are located at 443-570 nm with microsecond lifetimes (τ = 0.4-19.2 μs, ΦPL = 0.05-0.48). Complexes 2, 3, and 6 show prompt fluorescence, very weak yellowish green to yellow (λmax = 534-595 nm) emission with peak wavelengths at 534-595 nm, and lifetimes in nanoseconds (τ = 4.4-9.3 ns, ΦPL < 0.0001). (Metal + halide) to ligand and intraligand charge transitions are the main origin of the emission of the complexes. Solution-processed, complex-4-based nondoped and doped devices emit yellow green light with CIE coordinated at (0.41, 0.51), a maximum EQE up to 0.17%, and luminance reaching 75.52 cd/m2.

All-solution-processed multilayered white polymer light-emitting diodes (WPLEDs) are promising candidates for low-cost and large-area flexible full-color flat-panel displays and solid-state lightin...

A simple and efficient method for the regioselective thiolation of p-quinone methides with sodium aryl/alkyl sulfinates has been established using an acid/phosphine-induced radical route under transition-metal-free conditions. A broad range of sodium aryl/alkyl sulfinates and p-quinone methides (p-QMs) are compatible for the reaction, giving the expected products with good to excellent yields. Control experiments were also performed to gain insights into the generation mechanism of thiyl radicals and hydrogen-atom transfer process. This protocol provides a safe and feasible way for the formation of carbon-sulfur bonds.

A linear 5,15-di(naphthalimide) substituted porphyrin ZnD(p-NI)PP is facilely self-assembled into nanowires in solid with well-defined morphology through the synergistic π–π stack interactions of b...

A new family of pyrrolyl–acylhydrazones anchored with two BF2 units, named BOAPY, have been developed as BODIPY-like and unsymmetrical bis(BF2) chromophores via a simple one-pot reaction. The easil...

Two-dimensional (2D) nanorod meshes made of benzoperylene-1,3-dicyanotetrafluorobenzene (BP-1,3-DTFB) were formed via crystal transformation of the pre-existing BP microsheets. The transformation was driven by a cooperative effect of intermolecular charge-transfer and arene-perfluoroarene interactions. Epitaxial growth of cyan-emitting BP-1,3-DTFB nanorod meshes was directed by small lattice mismatch between BP and BP-1,3-DTFB, followed by the consumption of BP and the formation of BP-1,3-DTFB. Such a crystal transformation strategy can also be used to guide the formation of BP-1,4-dicyanotetrafluorobenzene (BP-1,4-DTFB) nanorod meshes. The present work reports a simple yet effective approach for the realization of aligned organic nanorod superstructures.

A new sublimable dicopper(I) complex bearing 1,2-bis(diphenylphosphino)ethane and 5-trifluoromethyl-3-(2'-pyridyl)pyrazolate ligands has been designed and synthesized, and its crystalline solvated and nonsolvated compounds have also been obtained and investigated. It is shown that only the crystalline solvated compound exhibits reversible and selective luminescence vapochromism, arising from its unique "pyridyl/CH

Phase-separated block copolymers (BCPs) that function as precursors to arrays of FePt nanoparticles (NPs) are of potential interest for the creation of media for the next-generation high-density magnetic data storage devices. A series of bimetallic BCPs has been synthesized by incorporating a complex containing Fe and Pt centers into the coordinating block of four different poly(styrene-b-4-vinylpyridine)s (PS-b-P4VPs, P1-P4). To facilitate phase separation for the resulting metalated BCPs (PM1-PM4), a loading of the FePt-bimetallic complex corresponding to ca. 20% was used. The bulk and thin-film self-assembly of these BCPs was studied by transmission electron microscopy (TEM) and atomic force microscopy, respectively. The spherical and cylindrical morphologies observed for the metalated BCPs corresponded to those observed for the metal-free BCPs. The products from the pyrolysis of the BCPs in bulk were also characterized by TEM, powder X-ray diffraction, and energy-dispersive X-ray spectroscopy, which indicated that the FePt NPs formed exist in an fct phase with average particle sizes of ca. 4-8 nm within a carbonaceous matrix. A comparison of the pyrolysis behavior of the metalated BCP (PM3), the metalated P4VP homopolymer (PM5), and the molecular model organometallic complex revealed the importance of using a nanostructured BCP approach for the synthesis of ferromagnetic FePt NPs with a smaller average NP size and a close to 1:1 Fe/Pt stoichiometric ratio.

Four platinum(II) complexes Pt-1, Pt-2, Pt-3, and Pt-4 with the isomeric donor-acceptor (D-A) conjugated ligand framework are designed and prepared, and their thermal, photophysical, and electrochemical characteristics investigated. Crystal structures for Pt-1 and Pt-4 are determined with single-crystal X-ray diffraction analysis, showing distorted and nonplanar geometry. Complex Pt-4 exhibits much greater distortion, attributed to the steric interactions between benzothiadiazole and naphthalene. Remarkably different photophysical, electrochemical, and electroluminescent properties are found for these platinum(II) complexes. Photoluminescence wavelengths of these complexes range from 590 to 800 nm with bandgaps of 1.7-2.0 eV. Coordination with [1,2,5]thiadiazolo[3,4- c]pyridine and triphenylamine can enhance D-A interactions, reducing the bandgap and producing near-infrared emission for Pt-3. Organic light-emitting devices (OLEDs) display electroluminescence with emission peaks at 626, 645, 826, and 571 nm, with maximum external quantum efficiencies of 0.13%, 0.04%, 0.49%, and 0.22% for Pt-1, Pt-2, Pt-3, and Pt-4 doped OLEDs, respectively. Thus, adjusting the coordination position with the isomeric conjugation framework ligand is an appropriate strategy to tune the light-emitting properties of platinum complexes in OLEDs.

For a highly efficient tandem organic solar cell, it is important for the subcells to minimize the absorption overlap and generate high and balanced currents. Considering the strong absorption and high external quantum efficiency at the short wavelength, developing a highly efficient blend system with a wide-bandgap (WBG) polymer as the donor and a fullerene derivative as the acceptor in the front cell would be an effective strategy. However, it is a challenge to obtain a high short-current density (Jsc) for this blend system. Here, we develop a WBG polymer (PBD1) with an optical bandgap of 1.88 eV. The PBD1:PC71BM blend system with a thickness of 230 nm achieves a power conversion efficiency (PCE) of 9.8% with a high Jsc of 14.6 mA cm–2. When tandem devices are fabricated with PBD1:PC71BM in the front cell, a PCE of 14.2% with a high Jsc of 12.3 mA cm–2 is achieved.

Heteroaryl incorporated acetylide-functionalized pyridinyl ligands (L1-L6) with the general formula Py-C≡C-Ar (Py = pyridine and Ar = thiophene-2-yl, 2,2' -bithiophene]-5-yl, 2,2' :5',2″ -terthiophene]-5-yl, thieno[2,3- b]thiophen-2-yl, quinoline-5-yl, benzo[c][1,2,5]thiadiazole-5-yl) have been synthesized by Pd(0)/Cu(I)-catalyzed cross-coupling reaction of 4-ethynylpyridine and the respective heteroaryl halide. Ligands L1-L6 were isolated in respectable yields and characterized by microanalysis, IR spectroscopy, 1H NMR spectroscopy, and ESI-MS mass spectrometry. A series of dinuclear Cu(I) complexes 1-10 have been synthesized by reacting L1-L6 with CuI and triphenylphosphine (PPh3) (R1) or with an anchored phosphine derivative, 4-(diphenylphosphino) benzoic acid (R2)/2-(diphenylphosphino)benzenesulfonic acid (R3), in a stoichiometric ratio. The complexes are soluble in common organic solvents and have been characterized by analytical, spectroscopic, and computational methods. Single-crystal X-ray structure analysis confirmed rhomboid dimeric structures for complexes 1, 2, 4, and 5, and a polymeric structure for 6. Complexes 1-6 showed oxidation potential responses close to 0.9 V vs Fc0/+, which were chemically irreversible and are likely to be associated with multiple steps and core oxidation. Preliminary photovoltaic (PV) results of these new materials indicated moderate power conversion efficiency (PCE) in the range of 0.15-1.56% in dye-sensitized solar cells (DSSCs). The highest PCE was achieved with complex 10 bearing the sulfonic acid anchoring functionality.

A fundamental, highly fluorescent, and easily accessible scaffold named BOPPY is reported. The use of hydrazine as a bridging linkage between pyrrole and N-heteroarenes enables the binding of two BF2 units to provide sufficient rigidity of the unsymmetric core skeleton. These resultant unsymmetrical BOPPYs are thus highly fluorescent in their solutions and solid powder states and exhibit high molar absorption coefficients (42200–47000 M–1 cm–1), large Stokes shifts, excellent photostability, and insensitivity to pH. More importantly, these BOPPYs showed efficient two-photon absorption in the wide spectral range of 700–900 nm, making them well suited for two-photon fluorescence microscopy imaging in living cells.

Cyclometalated Pt(II) complexes can show intense phosphorescence at room temperature. Their emission properties are determined by both the organic ligand and the metal center. Whereas most of the related studies focus on tuning the properties by designing different types of organic ligands, only several reports investigate the key role played by the metal center. To address this issue, phosphorescent Pt(II) complexes with one, two, and three Pt(II) centers are designed and synthesized. With more Pt(II) centers, the cyclometalated multinuclear Pt(II) complexes display red-shifted emissions with increased photoluminescence quantum yields. Most importantly, solution-processed organic light-emitting diodes (OLEDs) with the conventional device structure using the multinuclear Pt(II) complexes as emitters show excellent performance. The controlled device based on the conventional mononuclear Pt(II) complex shows a peak external quantum efficiency, current efficiency, and power efficiency of 6.4%, 14.4 cd A–1, a...

A new series of bimetallic Cu(I) complexes 1–5 triply bridged by a monoanionic or charge-neutral functionalized 3-(2′-pyridyl)-1,2,4-triazole in a μ–η1(N),η2(N,N) tridentate binding mode and two bis(diphenylphosphino)methane (dppm) ligands have been synthesized. Complexes 1–5 are singly or doubly charged dinuclear Cu(I) species with an eight-membered Cu2C2P4 ring of {Cu(μ-dppm)2Cu} unit, in which 3 and 4 adopt the boat–boat conformation, while 1, 2, and 5 display the chair–boat form. In these dimeric copper(I) complex cations, one of the two Cu(I) ions is four-coordinated, in a highly distorted N2P2 tetrahedral environment and the other is three-coordinated, in a distorted NP2 trigonal planar arrangement. All these Cu(I) complexes exhibit a comparatively weak low-energy absorption in CH2Cl2 solution, ascribed to the charge-transfer transitions with appreciable 1MLCT contribution, as suggested by time-dependent density functional theory (TDDFT) analyses. Complexes 1–5 display good emission properties in bo...

Real-time monitoring of the contents of molecular oxygen (O2) in tumor cells is of great significance in early diagnosis of cancer. At the same time, the photodynamic therapy (PDT) could be realized by highly toxic singlet oxygen (1O2) generated in situ during the O2 sensing, making it one of the most promising methods for cancer therapy. Herein, the iridium(III) complex cored hyperbranched phosphorescent conjugated polymer dots with the negative charges for hypoxia imaging and highly efficient PDT was rationally designed and synthesized. The incomplete energy transfer between the polyfluorene and the iridium(III) complexes realized the ratiometric sensing of O2 for the accurate measurements. Furthermore, the O2-dependent emission lifetimes are also used in photoluminescence lifetime imaging and time-gated luminescence imaging for eliminating the autofluorescence remarkably to enhance the signal-to-noise ratio of imaging. Notably, the polymer dots designed could generate the 1O2 effectively in aqueous sol...

In contrast to those for their polymeric counterparts, the controlled construction of organic heterostructured architectures derived from π-conjugated organic molecules has been rare and remains a great challenge. Herein, we develop a simple single-step solution strategy for the realization of organic heterostructures comprising coronene and perylene. Under a sequential crystallization process, an efficient doping step for coronene and perylene domains enables their perfect lattice matching, which facilitates facet-selective epitaxial growth of perylene domains on both the tips and the side surfaces of the preformed seed microwires by manipulating the growth pathways of the two pairs of materials. The present synthetic route provides a promising platform to investigate the detailed formation mechanism of complex organic heterostructures with specific topological configurations, further directing the construction of more functional heterostructured materials.

To mimic the natural photosynthetic systems utilizing chlorophylls to absorb light and store light energy, two new porphyrin-based small molecules of PTTR and PTTCNR have been developed for photovoltaic applications. The highest power conversion efficiency of 8.21% is achieved, corresponding to a short-circuit current of 14.30 mA cm–2, open-circuit voltage of 0.82 V, and fill factor of 70.01%. The excellent device performances can be ascribed to the engineering of molecule structure and film morphology. The horizontal conjugation of 3,3″-dihexyl-terthiophene to porphyrin-core with the vertical aliphatic 2-octylundecyl peripheral substitutions, can not only effectively increase the solar flux coverage between the conventional Soret and Q bands of porphyrin unit, but also optimize molecular packing through polymorphism associated with side-chains and the linear π-conjugated backbones. And the additive of 1,8-diiodooctane and subsequent chloroform solvent vapor annealing facilitate the formation of the blend...

Phosphorescent dinuclear iridium(III) complexes that can show high luminescent efficiencies and good electroluminescent abilities are very rare. In this paper, highly phosphorescent 2-phenylpyrimidine-based dinuclear iridium(III) complexes have been synthesized and fully characterized. Significant differences of the photophysical and electrochemical properties between the mono- and dinuclear complexes are observed. The theoretical calculation results show that the dinuclear complexes adopt a unique molecular orbital spatial distribution pattern, which plays the key role of determining their photophysical and electrochemical properties. More importantly, the solution-processed organic light-emitting diode (OLED) based on the new dinuclear iridium(III) complex achieves a peak external quantum efficiency (η(ext)) of 14.4%, which is the highest η(ext) for OLEDs using dinuclear iridium(III) complexes as emitters. Besides, the efficiencies of the OLED based on the dinuclear iridium(III) complex are much higher that those of the OLED based on the corresponding mononuclear iridium(III) complex.

Novel branching motif in hierarchical self-similar molecules: we present an under-explored class of molecules featuring striking geometric resemblance to the famous fractal of Sierpinski triangle. Unlike the more traditional, starburst dendrimers, the centripetal-shaped Sierpinski molecules feature side branches symmetrically bent away from the growth direction of the main branch, thus contrasting the natural-tree shape. Molecule G3 exhibits three distinct levels of structural hierachy comprising the primary, secondary and tertiary branches, while the smaller G2 contains only features of the 1st and 2nd orders. In spite of the much larger conjugated backbone of G3, its UV-vis absorption remains little shifted in wavelength compared to G2, while the emission of G3 is curiously blue-shifted by over 50 nm from that of G2.

A series of heteroleptic functional Ir(III) complexes bearing different fluorinated aromatic sulfonyl groups has been synthesized. Their photophysical features, electrochemical behaviors, and electroluminescent (EL) properties have been characterized in detail. These complexes emit intense yellow phosphorescence with exceptionally high quantum yields (ΦP0.9) at room temperature, and the emission maxima of these complexes can be finely tuned depending upon the number of the fluorine substituents on the pendant phenyl ring of the sulfonyl group. Furthermore, the electrochemical properties and electron injection/transporting (EI/ET) abilities of these Ir(III) phosphors can also be effectively tuned by the fluorinated aromatic sulfonyl group to furnish some desired characters for enhancing the EL performance. Hence, the maximum luminance efficiency (ηL) of 81.2 cd A(-1), corresponding to power efficiency (ηP) of 64.5 lm W(-1) and external quantum efficiency (ηext) of 19.3%, has been achieved, indicating the great potential of these novel phosphors in the field of organic light-emitting diodes (OLEDs). Furthermore, a clear picture has been drawn for the relationship between their optoelectronic properties and chemical structures. These results should provide important information for developing highly efficient phosphors.

A series of simple phenothiazine-based dyes have been synthesized, in which a cyanoacrylate acceptor directly attached to the C(3) position of phenothiazine, and an additional linear electron-rich (4-hexyloxy)phenyl group at C(7) on the opposite side of the acceptor, and an alkyl chain with different length at N(10) of the phenothiazine periphery are presented. The dye molecules have a linear shape which is favorable for the formation of a compact dye layer on the TiO2 surface, while their butterfly conformations can sufficiently inhibit molecular aggregation. Moreover, the structural features of (4-hexyloxy)phenyl donor moiety at the C(7) position of phenothiazine extends the π-conjugation of the chromophore, thus enhancing the performance of dye-sensitized solar cells (DSSCs). Moreover, the alkyl substituents with different chain length at the N(10) atom of phenothiazine could further optimize the performance through completely shielding the surface of TiO2 from the I–/I3- electrolyte and subsequently r...

Three new solution-processable platinum(II) polyyne polymers containing zinc(II) porphyrinate chromophores P1, P2, and P3 and their corresponding dinuclear model complexes were synthesized via the CuI-catalyzed dehydrohalogenation reaction of the platinum(II) chloride precursor and each of the respective bis(ethynyl)-zinc(porphyrin) metalloligands. The thermal, photophysical (absorption, excitation and emission spectra), electrochemical, and photovoltaic properties of P1–P3 were investigated. These results are also correlated by time-dependent density functional theory (TDDFT) calculations. The computations corroborate the presence of moderate conjugation in the π-systems, somewhat more accentuated for P3 where more favorable dihedral angles between the porphyrin and thiophene rings are noted. Moreover, the computed excited states are predicted to be π–π* in nature with some charge transfer components from the trans-[−C≡CPt(L)2C≡C−]n unit to the porphyrin rings. The optical bandgaps range from 1.93 to 2.0...

A water-soluble organometallic conjugated polyelectrolyte P1 and its corresponding model complex M1 based on an aspartic acid-substituted fluorene spacer are reported, which possess good water solubility as well as intriguing fluorescent and phosphorescent dual-emissive properties in a completely organic-free aqueous medium at room temperature. A new colorimetric silver ion sensor based on P1 is developed, which shows high selectivity and sensitivity for Ag+ ions in buffered water solution because of the Ag+-induced intersystem crossing from the singlet to triplet states. The obvious color change from colorless to yellow upon exposure to Ag+ ion is visible to the naked eyes and can be quantified colorimetrically by the visible absorption spectroscopic method. On the basis of the fluorescence intensity of P1 obtained in the fluorescence titration curves, a linear relationship is observed in the Stern−Volmer plot at low concentrations (1−5 μM), and the corresponding Stern−Volmer quenching constant (KSV) of ...

A series of soluble and thermally stable group 10 platinum(II) polyyne polymers of the type [−C≡C−Pt(PBu3)2−C≡C−Ar−Ox−Ar−]n (where Ox = 1,3,4-oxadiazole; Ar = p-C6H4 or 2,7-dihexyl-9,9-fluorene) and [−C≡C−Pt(PBu3)2−C≡C−Ar−Ox−Ar−Ox−Ar−]n (where Ar = 2,7-dihexyl-9,9-fluorene) along with their corresponding dinuclear model compounds [Ph−Pt(PEt3)2−C≡C−Ar−]2−Ox− (where Ar = p-C6H4 or 2,7-dihexyl-9,9-fluorene) and [Ph−Pt(PEt3)2−C≡C−Ar−Ox−]2−Ar− (where Ar = 2,7-dihexyl-9,9-fluorene) were prepared and characterized. The regiochemical structure of the polymers has been ascertained by single-crystal X-ray analysis on the model compound [Ph−Pt(PEt3)2−C≡C−p−C6H4−]2−Ox−. The photophysical properties (absorption, excitation, emission, and nanosecond transient absorption spectra) of these metalated compounds in 2MeTHF at 298 and 77 K are reported. These findings are correlated by density functional theory (DFT) calculations. Geometry optimizations predict totally planar molecules for these metalated complexes and polyme...

To model the performance of a bulk-heterojunction solar cell, it is necessary to obtain information about the index of refraction of the blend layer, which is typically determined by spectroscopic ellipsometry measurements. The optical functions of poly(3-hexylthiophene)−[6,6]-phenyl C61-butyric acid methyl ester (P3HT−PCBM) blend films have been extensively studied. However, there is a large variation of the reported optical functions in the literature. Because of this fact, as well as the widespread use of P3HT−PCBM films in organic photovoltaics, we have selected this material system as an example and performed a detailed analysis of spectroscopic ellipsometry data. We illustrate the occurrence of multiple solutions and the importance of a dedicated methodology to reach a satisfactory unique solution. The proposed methodology involves the following steps: (1) multisample analysis; (2) independent thickness and surface characterization; (3) use of the adequate optical description of substrate; (4) thick...

Energy remains one of the world's great challenges. Growing concerns about limited fossil fuel resources and the accumulation of CO(2) in the atmosphere from burning those fuels have stimulated tremendous academic and industrial interest. Researchers are focusing both on developing inexpensive renewable energy resources and on improving the technologies for energy conversion. Solar energy has the capacity to meet increasing global energy needs. Harvesting energy directly from sunlight using photovoltaic technology significantly reduces atmospheric emissions, avoiding the detrimental effects of these gases on the environment. Currently inorganic semiconductors dominate the solar cell production market, but these materials require high technology production and expensive materials, making electricity produced in this manner too costly to compete with conventional sources of electricity. Researchers have successfully fabricated efficient organic-based polymer solar cells (PSCs) as a lower cost alternative. Recently, metalated conjugated polymers have shown exceptional promise as donor materials in bulk-heterojunction solar cells and are emerging as viable alternatives to the all-organic congeners currently in use. Among these metalated conjugated polymers, soluble platinum(II)-containing poly(arylene ethynylene)s of variable bandgaps (∼1.4-3.0 eV) represent attractive candidates for a cost-effective, lightweight solar-energy conversion platform. This Account highlights and discusses the recent advances of this research frontier in organometallic photovoltaics. The emerging use of low-bandgap soluble platinum-acetylide polymers in PSCs offers a new and versatile strategy to capture sunlight for efficient solar power generation. Properties of these polyplatinynes--including their chemical structures, absorption coefficients, bandgaps, charge mobilities, accessibility of triplet excitons, molecular weights, and blend film morphologies--critically influence the device performance. Our group has developed a novel strategy that allows for tuning of the optical absorption and charge transport properties as well as the PSC efficiency of these metallopolyynes. The absorbance of these materials can also be tuned to traverse the near-visible and near-infrared spectral regions. Because of the diversity of transition metals available and chemical versatility of the central spacer unit, we anticipate that this class of materials could soon lead to exciting applications in next-generation PSCs and other electronic or photonic devices. Further research in this emerging field could spur new developments in the production of renewable energy.

A series of ruthenium(II) bis(8-quinolinolato) complexes bearing isocyanide ligands (RNC) have been synthesized by the reaction of [RuQ3] (Q = 8-quinolinolate) with RNC in the presence of Zn/Hg. These complexes have the general formula [RuQ2(RNC)2] (1, R = tert-butyl; 2, R = 4-MeOPh; 3, R = 4-ClPh; 4, R = 2,4,6-Br3Ph). Both the yellow cis,cis,trans (a) and orange-red trans,trans,trans (b) isomers have been isolated for complexes 1−4. trans,trans,trans-[Ru(Tol-Q)2(tBuNC)2] (6, HTol-Q = 8-hydroxyl-5-tolylquinoline) has also been prepared from [Ru(PPh3)2Cl2]. The structures of 2a, 3a, and 4b have been determined by X-ray crystallography. These complexes exhibit an intense absorption band in the UV region (λmax = 320−390 nm) with molar extinction coefficients (e) on the order of 104 dm3 mol−1 cm−1 and a moderately intense absorption with e on the order of 103 dm3 mol−1 cm−1 at 400−492 nm. The intense absorption at 320−390 nm is assigned to the ligand-centered π→π* transitions of the quinolinolate ligands, pro...

A series of soluble and thermally stable group 10 platinum(II) polyyne polymers of the type [−C≡C−Pt(PBu3)2−C≡C−X−]n along with their corresponding dinuclear model compounds [Ph−Pt(PEt3)2−C≡C]2−X− and [Ph3P−Au−C≡C]2−X− where X = F, Cz′, Cz, Cz−F, (Cz)2, (Cz)3 and Cz−F−Cz; F = 2,7-fluorene, Cz′ = 2,7-carbazole, Cz = 3,6-carbazole, were prepared and characterized. The electronic spectra (absorption, excitation, emission and ns transient absorption spectra) and the photophysical properties of these metalated compounds in 2MeTHF at 298 and 77 K are reported. These findings are correlated to the computational data obtained by density functional theory (DFT). Evidence for intramolecular singlet electron and triplet energy transfers from the Cz chromophore to the F moiety is provided and discussed in detail for those with organic spacers consisting of the carbazole−fluorene hybrids. The rate for electron transfer is very rapid (ket > 4 × 1011 s−1 at 298 K) whereas that for triplet−triplet energy transfer is much...

A series of single-stranded helical Re(I) complexes, of formula [Re(2)(L)Br(2)(CO)(6)], were prepared by reacting [Re(CO)(5)Br] with chiral quaterpyridines L1-4. By (1)H and (13)C NMR analysis, all the crude complexes consisted of a pair of stereoisomers. Sterically more demanding ligand L4 induced a higher ratio (80:20) than L1-3 (about 56:44). Stereochemically pure complexes could be obtained by recrystallization in CH(2)Cl(2). X-ray crystallographic analysis of single crystals from purified complexes showed a single-stranded helical structure with a bridging ligand wrapped around two distorted octahedral rhenium metals, both of which possessed one bromide ligand and three carbonyl ligands in a fac coordination. The helical core is established by extensive noncovalent electrostatic interactions and chiral information is transmitted from the ligand to the helix through these interactions. Solution behavior was studied by CD spectroscopy, and the strong Cotton effect confirms the integrity of the helical structure in solution. The diastereoselectivity of helicates is proposed to be induced by steric interaction between the bromine atom and the substituent of the bridging ligand.

The synthesis, characterization, and photophysics of a series of solution-processable and strongly visible-light absorbing platinum(II) polyynes containing bithiazole-oligo(thienyl) rings were presented. Tuning the polymer solar cell efficiency, as well as optical and charge transport properties, in soluble, low-band gap PtII-based conjugated poly(heteroaryleneethynylene)s using the number of oligothienyl rings is described. These materials are highly soluble in polar organic solvents due to the presence of solubilizing bithiazole moieties and show strong absorptions in the solar spectra, rendering them excellent candidates for bulk heterojunction polymer solar cells. Their photovoltaic responses and power conversion efficiencies (PCEs) depend to a large extent on the number of thienyl rings along the main chain, and some of them can be used to fabricate highly efficient solar cells with PCEs of up to 2.7% and a peak external quantum efficiency to 83% under AM1.5 simulated solar illumination, which is comparable to that of poly(3-hexylthiophene)-based devices fabricated without additional processing (annealing or TiO(x) layer). The influence of the number of thienyl rings and the metal group on the performance parameters and optimization of solar cell efficiency was evaluated and discussed in detail. At the same blend ratio of 1:4, the light-harvesting ability and PCE increase sharply as the thienyl chain length increases. The present work provides an attractive approach to developing conjugated metallopolymers offering broad solar absorptions and tunable solar cell efficiency and demonstrates the potential of metalated conjugated polymers for efficient power generation.

We introduce the 1,2,3-tris(organylthiophenyl) group as a symmetrical, multidentate chelation link for building coordination networks. For this, zinc(II) 5,10,15,20-tetrakis[3',4',5'-tris(methylthio)phenyl]porphyrin was synthesized and integrated into a two-dimensional network via coordination with BiBr3. The coordination link exhibits an unusually complex bonding pattern, involving six S atoms from two neighboring ligands that form multiple Bi-S interactions (distances ranging from 3.08 to 3.63 A) with a dimerlike unit of Bi2Br6. The electronic interaction between the porphyrin center and the Bi2Br6 block was illustrated by the diffuse-reflectance spectrum of the network compound, in which a modest red-shifted feature at 1.8 eV was seen (while the Q-band absorption of the metalloporphyrin core continues to be dominant at 1.9 eV).

Three new luminescent cyclometalated Pt(II) complexes, [Pt(L)Cl] (1), [Pt2(L-)2] (2), and [Pt(L)(PPh3)]ClO4 (3.ClO4) (where HL=2-phenyl-6-(1H-pyrazol-3-yl)-pyridine), were synthesized and characterized by X-ray crystallography. HL represents a new class of C,N,Npyrazolyl cyclometalating ligands containing a Cphenyl, a Npyridyl, and a Npyrazolyl donor moiety, as well as a 1-pyrazolyl-NH, that can also be available for metal coordination and other chemical interactions. Complex 1 possesses intense intraligand transitions at 275-375 nm and moderately intense metal-to-ligand charge transfer (1MLCT) (dpi(Pt)--pi*(L)) transition at 380-410 nm. The room temperature solid-state emission lambdamax of 1 occurs at 580 nm and is attributable to the 3MMLCT (dsigma*(Pt)--pi*(L)) transition. It also displays strong phosphorescence in acetonitrile solutions at room temperature with an emission lambdamax at 514 nm, which can be tentatively assigned to the 3MLCT (pi*(L)--dpi(Pt)) transition. Complex 1 can be deprotonated in organic solvents to yield a cycloplatinated dimer 2, which shows a relatively high room-temperature luminescent quantum yield of 0.59 in DMF (lambdamax=509 nm). Substitution of the ancillary chloro-ligand in 1 by triphenylphosphine yields 3, which also possesses a good room-temperature luminescent quantum yield of 0.52 in DMF (lambdamax=504 nm) and a better solubility in water. Complex 3 is synthesized to demonstrate the pH dependence of luminescent properties of this C,N,Npyrazolyl cyclometalated Pt(II) system. Such a pH response is ascribable to the protonation/deprotonation of the 1-pyrazolyl-NH on the C,N,Npyrazolyl cyclometalating ligand. The pKa of the 1-pyrazolyl-NH in 3, measured in 1:2 (v/v) aqueous DMF solutions, is approximately 4.0.

The synthesis and structural, photophysical, electrochemical, and electroluminescent properties of a novel class of trifunctional Pt(II) cyclometalated complexes are reported in which the hole-transporting triarylamine, electron-transporting oxadiazole, and electroluminescent metal components are integrated into a single molecule. These neutral metal chelates display good thermal stability (250 degrees C under N2) and morphological stability. All of them exhibit intense ligand-centered fluorescence and phosphorescence in fluid solutions at room temperature, but the emission spectra become largely dominated by triplet emission bands in CH2Cl2 glass at 77 K. Substituents with different electronic properties were introduced into the bipolar cyclometalating ligands to fine-tune the absorption and emissive characteristics of the compounds, and the results were correlated with theoretical calculations using density functional theory. A comparison of the photophysics and electrochemistry of our multifunctional systems to those only derived from each of the constituent components was also made and discussed. These Pt complexes can be vacuum-sublimed and applied as emissive dopants for the fabrication of vapor-deposited electrophosphorescent organic light-emitting devices (OLEDs), which generally exhibit good device performance with efficiencies up to 3.6%, 11.0 cd A-1, and 5.8 lm W-1. While the electroluminescence energy resembles that recorded in fluid solutions for these Pt emitters, these monochromatic OLEDs can emit tunable colors by varying the aryl ring substituents and the level of doping. Saliently, single dopant white-light electroluminescence, triggered by the simultaneous fluorescence/phosphorescence emission of the metal complexes and a variation of applied driving voltages, has also been realized based on some of these multifunctional complexes with peak electrophosphorescence efficiencies of 6.8 cd A-1 and 2.6%.

An efficient multilayer white organic light-emitting diode (WOLED) based on a new orange phosphorescent iridium complex [Ir(L)3] (HL = (9,9-diethyl-7-pyridinylfluoren-2-yl)diphenylamine) was fabricated. The WOLED device employs two emission layers in which one layer contains 5% [Ir(L)3] doped in the CBP host matrix (CBP = 4,4‘-N,N‘-dicarbazolebiphenyl) and another layer is composed of the mCP host (mCP = N,N‘-dicarbazolyl-3,5-benzene) doped with a 8% blue-emitting phosphor, iridum(III)bis(4,6-di-fluorophenyl)-pyridinato-N,C2)picolinate (FIrPic). The threshold voltage of the device is 4.2 V, and the brightness reaches 3200 cd/m2 at 10 V and 30 mA/cm2. The color of the white light corresponds to the Commission Internationale de L'Eclairage (CIE) coordinates of (0.31, 0.41) and a strong voltage dependence of the electroluminescence spectrum is observed, with the blue color intensity increasing relative to the orange component at increasing voltage. The maximum current efficiency of 17.8 cd/A and power effici...

We describe for the first time thermally stable and high-molecular-weight group 10 platinum(II) and group 12 mercury(II) polyyne polymers consisting of 2,7-bis(buta-1,3-diynyl)-9,9-dihexylfluorene linking units trans-[Pt(PBu3)2(C⋮C)2R(C⋮C)2]n and [Hg(C⋮C)2R(C⋮C)2]n (R = 9,9-dihexylfluorene-2,7-diyl). The optical absorption and photoluminescence spectra of these carbon-rich metallopolymers were examined and compared with their dinuclear model complexes trans-[Pt(Ph)(PEt3)2(C⋮C)2R(C⋮C)2Pt(Ph)(PEt3)2] and [MeHg(C⋮C)2R(C⋮C)2HgMe] as well as the group 11 gold(I) congener [(PPh3)Au(C⋮C)2R(C⋮C)2Au(PPh3)]. The regiochemical structures of the polymers were studied by NMR spectroscopy and ascertained by single-crystal X-ray structural analysis for the model platinum(II) compound. The heavy-atom effects of group 10−12 transition metals in triplet light energy harvesting and the influence of the C⋮C chain length on the spatial extent of singlet and triplet excitons in metalated systems of the form [M(C⋮C)mR(C⋮C)mM]n ...

Experimental investigations of the nonlinear optical transmittance characteristics of a series of solution-processable platinum polyyne polymers at 532 nm show that they are excellent optical limiters with performance comparable or superior to those of the state-of-the-art reverse saturable absorption dyes such as fullerene C60 and metal phthalocyanine complexes. On the basis of results from photophysical studies, both the inclusion of a platinum chromophore for increasing the intersystem crossing rate and the formation of an intramolecular charge-transfer state between the electron-withdrawing and electron-donating moieties along the polymer chain are very effective approaches for the enhancement of the optical-limiting properties of these metal polyynes. The structural influence of the aryl linker units on the optical-limiting action has been evaluated in detail. The optical-limiting thresholds for these polymetallaynes range from 0.06 to 0.15 J/cm2 at 82% linear transmittance, and these polymeric mater...

The synthesis of a novel trifunctional Pt(II) cyclometalated complex in which the hole-transporting (HT), electron-transporting (ET), and electroluminescent (EL) components are integrated into a single molecule is accomplished, and this complex can be sublimed and used for the fabrication of neat emissive layer electrophosphorescent devices.

Several soluble and well-defined copolymers of 9,9-dihexyl-2,7-fluorene and 9-aryl-3,6-carbazole (aryl = phenyl, p-methylphenyl, p-methoxyphenyl) were prepared in good yields by Suzuki-type coupling polymerization of fluorene−diboronic ester with some 9-aryl-3,6-dibromocarbazole derivatives. These copolymers showed high glass transition temperatures, and their regiochemical structures and physical properties were studied by gel permeation chromatography, NMR, UV absorption, elemental analysis, thermogravimetry, photoluminescence, and quantum yield measurements. The influence of the carbazole core and its aryl substituent on the photophysical, electrochemical, and electroluminescent properties of these alternating fluorene/carbazole copolymers has been investigated. Both the absorption and photoluminescence peaks of these copolymers are blue-shifted relative to the poly(9,9-dihexylfluorene) homopolymer (PF-C6), and cyclic voltammetry showed that these copolymers have their HOMO energy levels raised relativ...

A trinuclear heterobimetallic Ru(II)-Cu(II) donor-acceptor complex, [Ru(II)((t)Bubpy)(CN)(4)-[Cu(II)(dien)](2)](ClO(4))(2) ((t)Bubpy = 4,4'-di-tert-butyl-2,2'-bipyridine; dien = diethylenetriamine) (1), has been synthesized and successfully used as an chemodosimetric ensemble for the specific detection of cyanide in aqueous DMF. X-ray crystallography, solid and solution IR spectroscopy, and conductivity measurements reveal that complex 1 is a one-dimensional polymer in the crystalline state and dissociates into its [Ru(II)((t)Bubpy)(CN)(2)[(CN)Cu(II)(dien)L](2)](2+) (L = solvent) monomeric units in polar solvents. The MLCT transition and luminescence properties of the solvatochromic [Ru(II)((t)Bubpy)(CN)(4)](2)(-) donor are perturbed by the coordination of two Cu(II) acceptors but restored in the presence of CN(-). Spectroscopic and mass spectrometric studies confirm the cleavage of the cyano bridge between Ru(II) and Cu(II) of the chemodosimetric ensemble after the binding of cyanide to the Cu(II) centers. The overall binding constant, K(B), between 1 and CN(-) is measured to be (7.39 +/- 0.23) x 10(6) M(-2). A detection limit of 1.2 microM (0.03 ppm) of CN(-) in aqueous DMF (pH 7.4) is achievable. Thermodynamic evaluation shows that the analyte specificity of chemodosimeter 1 is attributable to the relative stability of the donor-acceptor complex to that of adducts formed between the acceptor metal center and the analytes.

Soluble and thermally stable group 10 platinum(II) and group 12 mercury(II) polyyne polymers containing the diphenylfluorene moiety trans-[−Pt(PBu3)2C⋮CRC⋮C−]n and [−HgC⋮CRC⋮C−]n (R = 9,9-diphenylf...