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A new sensing strategy towards hydrogen peroxide based on metal coordination polyelectrolyte‐driven self‐assembly of alkynylplatinum(II) 2,6‐bis(benzimidazol‐2′‐yl)pyridine (bzimpy) complex was demonstrated. The cationic in situ‐generated Ag(I)–thiocholine coordination polyelectrolytes were shown to induce the supramolecular self‐assembly of anionic low‐energy red‐emissive alkynylplatinum(II) bzimpy complexes via non‐covalent Pt(II)⋅⋅⋅Pt(II), electrostatic and π–π stacking interactions. The presence of hydrogen peroxide was shown to inhibit the formation of coordination polyelectrolytes and the coordination polyelectrolyte‐induced self‐assembly of platinum(II) complexes. The weakening of Pt(II)⋅⋅⋅Pt(II), electrostatic and π–π stacking interactions was supported by UV‐vis absorption, emission, and resonance light scattering (RLS) studies. The present assay was also applied to probe glucose indirectly based on the enzymatic reaction of glucose oxidase on the substrate. Operating in a label‐free manner, together with the low‐energy red emission and large Stokes shift of alkynylplatinum(II) complexes, these features render the proposed design attractive for biological applications. [ABSTRACT FROM AUTHOR]

Two challenges remain for organic thermoresponsive materials; one is to develop high‐performance red‐emissive thermoresponsive materials, while another is to simultaneously achieve high contrast ratio (CR), fast and reversible thermoresponse in a single element. Herein, we not only develop a new deep‐red emissive squaraine‐based AIEgen (TPE‐SQ12) based on a pyrylium end group, which is suitable for fabricating high‐performance thermoresponsive materials, but also show an effective approach to improve both CR (∼ten times increase) and response time (less than 3 seconds), that is, molecularly dispersing AIEgen into an elastomer, attributed to the significantly expanded free volume of elastomer upon increasing the temperature that can activate the AIEgen intramolecular movements more pronouncedly. Double encryption and temperature mapping systems have been separately established by using our designed elastomer/TPE‐SQ12 film, showing the great potential for anti‐counterfeiting and temperature sensing. Finally, white emission is further achieved by co‐doping TPE‐SQ12 with cyan dye into elastomer, which enables fluorescent thermochromism for improving the temperature mapping ability. [ABSTRACT FROM AUTHOR]

Since 2014, we have introduced in literature the use of phenylglyoxylic acid (PhCOCOOH), a small and commercially available organic molecule, as a potent promoter in a variety of photochemical processes. Although PhCOCOOH has a broad scope of photochemical reactions that can promote, the understanding of its mode of action in our early contributions was moderate. Herein, we are restudying and revisiting the mechanism of action of PhCOCOOH in most of these early contributions, providing a unified mechanism of action. Furthermore, the understanding of its action as a photoinitiator opened a new comparison study with known and commercially available photoinitiators. [ABSTRACT FROM AUTHOR]

Three new aza‐BODIPY dyes incorporating fused fluorene or carbazole moieties have been prepared. The dyes show significant enhancement of photophysical properties compared to the parent 1,3,5,7‐tetraphenyl aza‐BODIPY (TPAB): a bathochromic shift of the absorption maximum (up to 2700 cm−1) and emission maximum (up to 2270 cm−1); an almost threefold increase in molar absorption coefficients (to ca. 230 000 M−1 cm−1) and a significant increase in the fluorescence quantum yield to 49–66 %. Owing to the combination of these properties, the new aza‐BODIPY dyes belong to the brightest NIR dyes reported. The dyes also show excellent photostability. Due to their outstanding properties, the new dyes represent a promising platform for further exploration in biomedical research. A pH indicator containing only one fused carbazole unit was also prepared and shows absorption and emission spectra that are bathochromically shifted by about 110 and 100 nm, respectively, compared to the indicator dye based on the TPAB chromophore. [ABSTRACT FROM AUTHOR]

Phosgene and its substitutes (diphosgene and triphosgene) are widely utilized as chemical industrial materials and chemical warfare agents and pose a threat to public health and environmental safety due to their extreme toxicity. Research efforts have been directed to develop selective and sensitive detection methods for phosgene and its substitutes. In this paper, we have prepared two BODIPY‐based fluorescent probes, o‐Pah and o‐Pha, which are two isomers with different active sites, ortho‐aminohydroxy (3′,4′ or 4′,3′) phenyls at meso position of BODIPY, and compared their sensing performance toward triphosgene. The probe with o‐(4′‐amino‐3′‐hydroxyl), o‐Pha, exhibits better sensing performance over the o‐(3′‐amino‐4′‐hydroxyl), o‐Pah, for instance, a lower limit of detection (LOD) (0.34 nm vs. 1.2 nm), and more rapid response (10 s vs. 200 s). Furthermore, based on the above comparative studies, a red‐fluorescence probe o‐Phae has been constructed through extending 3,5‐conjugation of o‐Pha. The probe o‐Phae displays rapid response (60 s), high sensitivity to triphosgene (LOD=0.88 nm), and high selectivity for triphosgene over relevant analytes including nitric oxide. Finally, a facile test strip for phosgene was fabricated by immobilizing o‐Phae in a polyethylene oxide membrane for sensitive (<2 ppm) and selective detection of phosgene in the gas phase. [ABSTRACT FROM AUTHOR]

Live‐cell imaging with fluorescent probes is an essential tool in chemical biology to visualize the dynamics of biological processes in real‐time. Intracellular disease biomarker imaging remains a formidable challenge due to the intrinsic limitations of conventional fluorescent probes and the complex nature of cells. This work reports the in cellulo assembly of a fluorescent probe to image cyclooxygenase‐2 (COX‐2). We developed celecoxib‐azide derivative 14, possessing favorable biophysical properties and excellent COX‐2 selectivity profile. In cellulo strain‐promoted fluorogenic click chemistry of COX‐2‐engaged compound 14 with non/weakly‐fluorescent compounds 11 and 17 formed fluorescent probes 15 and 18 for the detection of COX‐2 in living cells. Competitive binding studies, biophysical, and comprehensive computational analyses were used to describe protein‐ligand interactions. The reported new chemical toolbox enables precise visualization and tracking of COX‐2 in live cells with superior sensitivity in the visible range. [ABSTRACT FROM AUTHOR]

The development of novel methodologies for the functionalization of saturated heterocycles is highly desirable. Herein, we report a cheap and efficient photochemical method for the C−H functionalization of saturated O‐heterocycles, as well as the deconstructive ring‐cleavage of S‐heterocycles, employing hypervalent iodine alkynylation reagents (ethynylbenziodoxolones, EBX). This photochemical alkynylation is performed utilizing phenylglyoxylic acid as the photoinitiator, leading to the corresponding products in good to high yields, under household fluorescent light bulb irradiation. When O‐heterocycles were employed, the expected α‐C−H alkynylation took place. In contrast, oxidative ring‐opening to form a thioalkyne and an aldehyde was observed with S‐heterocycles. Preliminary mechanistic experiments are presented to give first insights into this puzzling divergent reactivity. [ABSTRACT FROM AUTHOR]

A novel class of phosphorescent cationic heterobimetallic IrIII/MI complexes, where MI=CuI (4) and AuI (5), is reported. The two metal centers are connected by the hybrid bridging 1,3‐dimesityl‐5‐acetylimidazol‐2‐ylidene‐4‐olate (IMesAcac) ligand that combines both a chelating acetylacetonato‐like and a monodentate N‐heterocyclic carbene site coordinated onto an IrIII and a MI center, respectively. Complexes 4 and 5 have been prepared straightforwardly by a stepwise site‐selective metalation with the zwitterionic [(IPr)MI(IMesAcac)] metalloproligand (IPr=1,3‐(2,6‐diisopropylphenyl)‐2H‐imidazol‐2‐ylidene) and they have been fully characterized by spectroscopic, electrochemical, and computational investigation. Complexes 4 and 5 display intense red emission arising from a low‐energy excited state that is located onto the "Ir(C^N)" moiety featuring an admixed triplet ligand‐centered/metal‐to‐ligand charge transfer (3IL/1MLCT) character. Comparison with the benchmark mononuclear complexes reveals negligible electronic coupling between the two distal metal centers at the electronic ground state. The bimetallic systems display enhanced photophysical properties in comparison with the parental congeners. Noteworthy, similar non‐radiative rate constants have been determined along with a two‐fold increase of radiative rate, yielding brightly red‐emitting cyclometalating IrIII complexes. This finding is ascribed to the increased MLCT character of the emitting state in complexes 4 and 5 due to the smaller energy gap between the 3IL and 1MLCT manifolds, which mix via spin–orbit coupling. [ABSTRACT FROM AUTHOR]

Two photoactivatable dicarbonyl ruthenium(II) complexes based on an amide‐functionalised bipyridine scaffold (4‐position) equipped with an alkyne functionality or a green‐fluorescent BODIPY (boron‐dipyrromethene) dye have been prepared and used to investigate their light‐induced decarbonylation. UV/Vis, FTIR and 13C NMR spectroscopies as well as gas chromatography and multivariate curve resolution alternating least‐squares analysis (MCR‐ALS) were used to elucidate the mechanism of the decarbonylation process. Release of the first CO molecule occurs very quickly, while release of the second CO molecule proceeds more slowly. In vitro studies using two cell lines A431 (human squamous carcinoma) and HEK293 (human embryonic kidney cells) have been carried out in order to characterise the anti‐proliferative and anti‐apoptotic activities. The BODIPY‐labelled compound allows for monitoring the cellular uptake, showing fast internalisation kinetics and accumulation at the endoplasmic reticulum and mitochondria. [ABSTRACT FROM AUTHOR]

Synthesis, characterization, electrochemistry, and photophysics of homo‐ and heteroleptic ruthenium(II) complexes [Ru(cpmp)2]2+ (22+) and [Ru(cpmp)(ddpd)]2+ (32+) bearing the tridentate ligands 6,2"‐carboxypyridyl‐2,2'‐methylamine‐pyridyl‐pyridine (cpmp) and N,N'‐dimethyl‐N,N'‐dipyridin‐2‐ylpyridine‐2,6‐diamine (ddpd) are reported. The complexes possess one (32+) or two (22+) electron‐deficient dipyridyl ketone fragments as electron‐accepting sites enabling intraligand charge transfer (ILCT), ligand‐to‐ligand charge transfer (LL'CT) and low‐energy metal‐to‐ligand charge transfer (MLCT) absorptions. The latter peak around 544 nm (green light). Complex 22+ shows 3MLCT phosphorescence in the red to near‐infrared spectral region at room temperature in deaerated acetonitrile solution with an emission quantum yield of 1.3 % and a 3MLCT lifetime of 477 ns, whereas 32+ is much less luminescent. This different behavior is ascribed to the energy gap law and the shape of the parasitic excited 3MC state potential energy surface. This study highlights the importance of the excited‐state energies and geometries for the actual excited‐state dynamics. Aromatic and aliphatic amines reductively quench the excited state of 22+ paving the way to photocatalytic applications using low‐energy green light as exemplified with the green‐light‐sensitized thiol–ene click reaction. [ABSTRACT FROM AUTHOR]

A series of new 5‐mono‐ and 5,5′‐bisamino‐substituted azothiazole derivatives was synthesized from the readily available diethyl azothiazole‐4,4′‐dicarboxylate. This reaction most likely comprises an initial Michael‐type addition by the respective primary alkyl and aromatic amines at the carbon atom C5 of the substrate. Subsequently, the resulting intermediates are readily oxidized by molecular oxygen to afford the amino‐substituted azothiazole derivatives. The latter exhibit remarkably red‐shifted absorption bands (λabs=507–661 nm) with high molar extinction coefficients and show a strong positive solvatochromism. As revealed by spectrometric titrations and circular and linear dichroism studies, the water‐soluble, bis‐(dimethylaminopropylamino)‐substituted azo dye associates with duplex DNA by formation of aggregates along the phosphate backbone at high ligand–DNA ratios (LDR) and by intercalation at low LDR, which also leads to a significant increase of the otherwise low emission intensity at 671 nm. [ABSTRACT FROM AUTHOR]

The hetero‐Pacman architecture places two different metal coordination sites in close proximity, which can support efficient energy and/or electron transfer and allow for cooperative activation of small molecules. Here, the synthesis of dyads consisting of a porphyrin unit as photosensitizer and a rhenium unit as catalytically active site, which are held together by the rigid xanthene backbone, is presented. Mononuclear [(NN)Re(CO)3(Cl)] complexes for CO2 reduction in which NN represents a bidentate diimine ligand (e.g. bipyridine or phenanthroline) lack light absorption in the visible region, resulting in poor photocatalysis upon illumination with visible light. To improve their visible‐light absorption, we have focused on the incorporation of a strongly absorbing free base or zinc porphyrin unit. Resulting photocatalytic experiments showed a strong dependence of the catalytic performance on both the type of photosensitizer and the excitation wavelengths. Most notably, the intramolecular hetero‐Pacman system containing a zinc porphyrin unit showed much better catalytic activity in the visible region (excitation wavelengths >450 nm) than the free base porphyrin version or the corresponding mononuclear rhenium compound or an intermolecular system comprised of a 1:1 mixture of the mononuclear analogues. The hetero‐Pacman architecture places a porphyrin and a rhenium terpyridine unit in close distance to each other. This molecular design allows for wavelength‐independent light‐driven activation of CO2 when a zinc porphyrin unit is used as photosensitizer. Time‐resolved spectroscopic measurements confirmed the electronic communication between the two functional units and suggested the involvement of a charge‐separated state. [ABSTRACT FROM AUTHOR]

Bis(acetylido) aurates(I) and thallium(I) trifluoromethylsulfonates were used to synthesize AuI–TlI metallopolymers, displaying novel and unusual structural motifs of the metal–metal backbones in the solid state: a discrete molecular cluster, 1D chains of interconnected dimers, tetramers, or dodecamers of Au–Tl units, and a 2D‐plane network, consisting of alternating edge‐linked (AuTl)6 and (AuTl)4 cycles. The formation of the different architectures was primarily controlled by the steric demand of the acetylide‐substituent groups. Thus, the bulkiest 2,6‐diisopropylphenyl derivative yielded a molecular cluster [Tl2Au3]. Most compounds showed bright visible photoluminescence with quantum yields of up to 25 % at ambient temperature. The color of the emitted light significantly differs with the network structure. Furthermore, theoretical studies of singlet excitations in the molecular cluster, as well as NMR and mass‐spectrometric investigations of the fragmentation of the metallopolymers in solution are described in detail. Bigger for better or worse: Luminescent AuI–TlI metallopolymers, displaying novel and unusual structural motifs of the metal–metal backbones in the solid state, are reported. [ABSTRACT FROM AUTHOR]

The synthesis and the photophysical properties of a new class of fully organic monodisperse nanoparticles for combined two‐photon imaging and photodynamic therapy are described. The design of such nanoparticles is based on the covalent immobilization of a dedicated quadrupolar dye that combines excellent two‐photon absorbing (2PA) properties, fluorescence and singlet oxygen generation ability, in a phosphorous‐based dendrimeric architecture. First, a bifunctional quadrupolar dye bearing two different grafting moieties, a phenol function and an aldehyde function, was synthesized. It was then covalently grafted through its phenol function to a phosphorus‐based dendrimer scaffold of generation 1. The remaining aldehyde functions were then used to continue the dendrimer synthesis up to generation 2, introducing finally 24 water‐solubilizing triethyleneglycol chains at its periphery. A dendrimer confining 12 photoactive quadrupolar units in its inner scaffold and showing water solubility was thus obtained. Interestingly, the G1 and G2 dendrimers retain some fluorescence as well as significant singlet oxygen production efficiencies while they were found to show very high 2PA cross‐sections in a broad range of the NIR biological spectral window. Hydrophilic dendrimer G2 was tested in vitro on breast cancer cells, first in one‐ and two‐photon microscopy, which allowed for visualization of their cell internalization, then in two‐photon photodynamic therapy. While being nontoxic in the dark and, more importantly, under exposure to daylight, dendrimer G2 proved to be a very efficient cell‐death inducer only under two‐photon irradiation in the NIR. (Cell) death by day or night: New dendrimers combining high two‐photon brightness and photosensitizing properties are efficient cell‐death inducers under two‐photon irradiation in the NIR, while being non‐toxic in the dark and under exposure to daylight. [ABSTRACT FROM AUTHOR]

Abstract: Although the strain‐promoted sydnone–alkyne cycloaddition reaction has been utilized for bioconjugation, its potential applications in bioorthogonal labeling and imaging in live cells have not been explored. This communication reports novel bioorthogonal imaging reagents with environment‐sensitive emission properties through the modification of sydnone with cyclometalated iridium(III) polypyridine complexes. These complexes displayed significant emission enhancement and lifetime elongation upon reaction with strained alkyne derivatives, and were utilized to label cyclooctyne‐modified proteins and ceramide molecules in live cells. Additionally, the manipulation of the photocytotoxicity of the complexes through the use of a bioorthogonal reagent was demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: A CuI bis‐phenanthroline rotaxane was prepared by using the [2+2] cycloaddition‐retroelectrocyclization (CA‐RE) reaction to graft a bulky dicyanoquinodimethane (DCNQ) stopper. The electronic properties were investigated with electrochemical and photophysical techniques, in parallel with three reference compounds, namely, the DCNQ derivative alone, the DCNQ‐based phenanthroline ligand, and an analogue CuI complex lacking the DCNQ moiety. In all the systems containing the DCNQ unit, the lowest electronic excited states are centered thereon, with the singlet level (S1) located at about 1.0 eV, as suggested by TDDFT calculations. Accordingly, in the DCNQ‐equipped rotaxane, the typical metal‐to‐ligand charge‐transfer luminescence of the CuI center is totally quenched. Ultrafast transient absorption and emission studies show that, in the rotaxane, the final sink of photoinduced processes is the lowest singlet state of the DCNQ moiety (S1), which exhibits strong charge‐transfer character and a lifetime of 0.4 ps. Its deactivation leads to population of another excited state with a lifetime of 1.3 ps, which can be the related triplet state (T1) or a vibrationally hot level (hot‐S0). Notably, S1 also shows stimulated fluorescence in the near‐infrared (NIR) region between 1100 and 1500 nm, corroborating the TDDFT prediction. This unusual finding opens up the study of ultrashort‐lived NIR luminescence in organic donor–acceptor systems. [ABSTRACT FROM AUTHOR]

Abstract: Selective C−H activation is an area of growing importance. Metal‐free C−H activation of branched aldehydes mediating the hydroacylation of electron‐deficient alkenes is an attractive transformation, but is limited by selectivity issues, especially in the case of α,α‐disubstituted aldehydes. Herein, we report a green, cheap, versatile, and easily reproducible selective hydroacylation of alkenes utilizing phenylglyoxylic acid as the photocatalyst and common household bulbs for irradiation, leading to products in excellent yields and selectivities. The reaction mechanism was also studied to account for the high selectivity. [ABSTRACT FROM AUTHOR]

A family of five neutral cyclometalated iridium(III) tetrazolato complexes and their methylated cationic analogues have been synthesised and characterised. The complexes are distinguished by variations of the substituents or degree of π conjugation on either the phenylpyridine or tetrazolato ligands. The photophysical properties of these species have been evaluated in organic and aqueous media, revealing predominantly a solvatochromic emission originating from mixed metal-to-ligand and ligand-to-ligand charge transfer excited states of triplet multiplicity. These emissions are characterised by typically long excited-state lifetimes (∼hundreds of ns), and quantum yields around 5-10 % in aqueous media. Methylation of the complexes caused a systematic red-shift of the emission profiles. The behaviour and the effects of the different complexes were then examined in cells. The neutral species localised mostly in the endoplasmic reticulum and lipid droplets, whereas the majority of the cationic complexes localised in the mitochondria. The amount of complexes found within cells does not depend on lipophilicity, which potentially suggests diverse uptake mechanisms. Methylated analogues were found to be more cytotoxic compared to the neutral species, a behaviour that might to be linked to a combination of uptake and intracellular localisation. [ABSTRACT FROM AUTHOR]

The dyads 1- 3 made of an alkynylated ZnII-porphyrin and a bis-methanofullerene derivative connected through a copper-catalyzed azide-alkyne cycloaddition have been synthesized. The porphyrin and fullerene chromophores are separated through a bridge made of a bismethanofullerene tether linked to different spacers conjugated to the porphyrin moiety [i.e., m-phenylene ( 1), p-phenylene ( 2), di- p-phenylene-ethynylene ( 3)]. Compounds 1- 3 exhibit relatively rigid structures with an interchromophoric separation of 1.7, 2.0, and 2.6 nm, respectively, and no face-to-face or direct through-bond conjugation. The photophysical properties of compounds 1- 3 have been investigated in toluene and benzonitrile with steady-state and time-resolved techniques as well as model calculations on the Förster energy transfer. Excited-state interchromophoric electronic interactions are observed with a distinct solvent and distance dependence. The latter effect is evidenced in benzonitrile, where compounds 1 and 2 exhibit a photoinduced electron transfer in the Marcus-inverted region, with charge-separated (CS) states living for 0.44 and 0.59 μs, respectively, whereas compound 3 only undergoes energy transfer, as in apolar toluene. The quantum yield of the charge separation (φCS) of compounds 1 and 2 in benzonitrile is ≥0.75. It is therefore demonstrated that photoinduced energy and electron transfers in porphyrin-fullerene systems with long interchromophoric distances may efficiently occur also when the bridge does not provide a wire-like conjugation and proceed through the triplet states of the chromophoric moieties. [ABSTRACT FROM AUTHOR]

Diaminoterephthalates are fluorescent dyes and define scaffolds, which can be orthogonally functionalized at their two carboxylate residues with functional residues bearing task specific reactive groups. The synthesis of monofunctionalized dyes with thiol groups for surface binding, an azide for click chemistry, and a biotinoylated congener for streptavidin binding is reported. Two bifunctionalized dyes were prepared: One with an azide for click chemistry and a biotin for streptavidin binding, the other with a maleimide for reaction with thiol and a cyclooctyne moiety for ligation with copper-free click chemistry. In general, the compounds are red to orange, fluorescent materials with an absorption at about 450 nm and an emission at 560 nm with quantum yields between 2-41 %. Of particular interest is the maleimide-functionalized compound, which shows low fluorescence quantum yield (2 %) by itself. After addition of a thiol, the fluorescence is 'turned on'; quantum yield 41 %. [ABSTRACT FROM AUTHOR]

The intermolecular electrochemiluminescence resonance energy transfer (ECL-RET) between luminol and Ru(bpy)32+ was studied extensively to achieve the sensitive bioanalysis owing to the perfect spectral overlap of the donor and acceptor, but it still suffers from the challenging issue of low energy-transfer efficiency. The intramolecular ECL-RET towards the novel ECL compound containing the donor of luminol and the acceptor of Ru(bpy)2(mcpbpy)2+ (Lum-Ru) was designed and investigated. With the high-efficient ECL-RET in one molecule, the highly intense ECL signal of Lum-Ru was obtained owing to the short path of energy transmission and less energy loss between luminol and Ru(bpy)2(mcpbpy)2+. Lum-Ru was further applied to construct a signal-off electrochemiluminescence (ECL) aptasensor for ultrasensitive detection of a harsh carcinogen of Aflatoxin M1 (AFM1). This sensing platform also provides a significant boost for the trace detection of other biomolecules in clinical analysis. [ABSTRACT FROM AUTHOR]

The development of highly selective sensors for potassium is of great interest in biology. Two new hydrosoluble potassium sensors (Calix-COU-Alkyne and Calix-COU-Am) based on a calix[4]arene bis(crown-6) and an extended coumarin were synthesized and characterized. The photophysical properties and complexation studies of these compounds have been investigated and show high molar extinction coefficients and high fluorescence quantum yields. Upon complexation with potassium in the millimolar concentration range, an increase of one- and two-photon fluorescence emission is detected. A twofold fluorescence enhancement is observed upon excitation at λ=405 nm. The ligands present excellent selectivity for potassium in the presence of various competitive cations in water and in a physiological medium. The photophysical properties are not affected by the presence of a large amount of competing cations (Na+, Ca2+, Mg2+, etc.). Ex vivo measurements on mouse hippocampal slices show that Calix-COU-Alkyne accumulates extracellularly and does not alter the neuronal activity. Furthermore, the sensor can be utilized to monitor slow extracellular K+ increase induced by inhibition of K+ entry into the cells. [ABSTRACT FROM AUTHOR]

A series of symmetric fluorescent dyes built from a spirofluorene core bearing electroactive end groups and having different conjugated linkers were prepared with a view to their use as building blocks for the preparation of electrochemiluminescent (ECL) dyes and nanoparticles. Their electrochemical, spectroelectrochemical, and ECL properties were first investigated in solution, and structure/activity relationships were derived. The electrochemical and ECL properties show drastic variation that could be tuned by means of the nature of the π-conjugated system, the end groups, and the core. In this series, highly fluorescent dye 1 based on a spirofluorene core and triphenylamine end groups connected via thiophene moieties shows the most promising and intriguing properties. Dye 1 is reversibly oxidized in three well-separated steps and generates a very intense and large ECL signal. Its ECL efficiency is 4.5 times higher than that of the reference compound [Ru(bpy)3]2+ (bpy=2,2′-bipyridine). This remarkably high efficiency is due to the very good stability of the higher oxidized states and it makes 1 a very bright organic ECL luminophore. In addition, thanks to its molecular structure, this dye retains fluorescence after nanoprecipitation in water, which leads to fluorescent organic nanoparticles (FONs). The redox behavior of these FONs shows oxidation waves consistent with the initial molecular species. Finally, ECL from FONs made of 1 was recorded in water and strong ECL nanoemitters are thus obtained. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of four new tetracyanobutadiene (TCBD) derivatives (1-3 and 2') incorporating 2- or 2,7-fluorenyl and diphenylamino moieties are reported. The electroactivity of 1-3 and 2' was studied by cyclic voltammetry (CV), while the linear optical and (thirdorder) nonlinear optical (NLO) properties were investigated by electronic spectroscopy and Z-scan studies, respectively. All experimental investigations were rationalized by DFT computations, providing an insight into the electronic structure of these derivatives and on their application potential. We show that these derivatives are nonluminescent in solution at ambient temperatures, but become fluorescent in solvent glasses. This finding constitutes an unprecedented observation for TCBD derivatives. Also, we show by Z-scan studies that these derivatives behave as two-photon absorbers in the near-IR range (800-1050 nm). These third-order NLO properties are discussed and compared with those of their alkynyl precursors (4-6), which have been investigated by two-photon excited fluorescence (TPEF). [ABSTRACT FROM AUTHOR]

Elucidation of relationship among chemical structure, cellular uptake, localization, and biological activity of anticancer metal complexes is important for the understanding of their mechanisms of action. Organometallic rhenium(I) tricarbonyl compounds have emerged as potential multifunctional anticancer drug candidates that can integrate therapeutic and imaging capabilities in a single molecule. Herein, two mononuclear phosphorescent rhenium(I) complexes (Re1 and Re2), along with their corresponding dinuclear complexes (Re3 and Re4), were designed and synthesized as potent anticancer agents. The subcellular accumulation of Re1-Re4 was conveniently analyzed by confocal microscopy in situ in live cells by utilizing their intrinsic phosphorescence. We found that increased lipophilicity of the bidentate ligands could enhance their cellular uptake, leading to improved anticancer efficacy. The dinuclear complexes were more potent than the mononuclear counterparts. The molecular anticancer mechanisms of action evoked by Re3 and Re4 were explored in detail. Re3 with a lower lipophilicity localizes to lysosomes and induces caspase-independent apoptosis, whereas Re4 with higher lipophilicity specially accumulates in mitochondria and induces caspase-independent paraptosis in cancer cells. Our study demonstrates that subcellular localization is crucial for the anticancer mechanisms of these phosphorescent rhenium(I) complexes. [ABSTRACT FROM AUTHOR]

In this work, an 'on-off-on' switch system has been successfully applied through the construction of an electrochemiluminscent biosensor for copper ion (Cu2+) detection based on a new electrochemiluminescence (ECL) emitter of supramolecular nanorods, which was achieved through supramolecular interactions between 3,4,9,10-perylenetetracarboxylic acid (PTCA) and aniline. The initial 'signal-on' state with strong and stable ECL emission was obtained by use of the supramolecular nanorods with a new signal amplification strategy involving a co-reaction accelerator. In addition, ECL quencher probes (Fc-NH2/Cu-Sub/nano-Au) were fabricated by immobilizing aminoferrocene (Fc-NH2) on Cu-substrate strand modified Au nanoparticles. The quencher probes were hybridized with the immobilized Cu-enzyme strand to form Cu2+-specific DNAzyme. Similarly, the 'signal-off' state was obtained by the high quenching effect of Fc-NH2 on the ECL of the excited-state PTCA (1PTCA*). As expected, the second 'switch-on' state could achieved by incubating with the target Cu2+, owing to the Cu2+-specific DNAzyme, which was irreversibly cleaved, resulting in the release of the quencher probes from the sensor interface. Herein, on the basis of the ECL intensity changes (Δ IECL) before and after incubating with the target Cu2+, the prepared Cu2+-specific DNAzyme-based biosensor was used for the determination of Cu2+ concentrations with high sensitivity, excellent selectivity, and good regeneration. [ABSTRACT FROM AUTHOR]

Elucidation of relationship among chemical structure, cellular uptake, localization, and biological activity of anticancer metal complexes is important for the understanding of their mechanisms of action. Organometallic rhenium(I) tricarbonyl compounds have emerged as potential multifunctional anticancer drug candidates that can integrate therapeutic and imaging capabilities in a single molecule. Herein, two mononuclear phosphorescent rhenium(I) complexes ( Re1 and Re2), along with their corresponding dinuclear complexes ( Re3 and Re4), were designed and synthesized as potent anticancer agents. The subcellular accumulation of Re1-Re4 was conveniently analyzed by confocal microscopy in situ in live cells by utilizing their intrinsic phosphorescence. We found that increased lipophilicity of the bidentate ligands could enhance their cellular uptake, leading to improved anticancer efficacy. The dinuclear complexes were more potent than the mononuclear counterparts. The molecular anticancer mechanisms of action evoked by Re3 and Re4 were explored in detail. Re3 with a lower lipophilicity localizes to lysosomes and induces caspase-independent apoptosis, whereas Re4 with higher lipophilicity specially accumulates in mitochondria and induces caspase-independent paraptosis in cancer cells. Our study demonstrates that subcellular localization is crucial for the anticancer mechanisms of these phosphorescent rhenium(I) complexes. [ABSTRACT FROM AUTHOR]

A series of enantiomeric 2,6-bis(1,2,3-triazol-4-yl)pyridines (btp)-containing ligands was synthesized by a one-pot two-step copper-catalyzed amine/alkyne click reaction. The EuIII- and TbIII-directed self-assembly formation of these ligands was studied in CH3CN by monitoring their various photophysical properties, including their emerging circular dichroism and circularly polarized luminescence. The global analysis of the former enabled the determination of both the stoichiometry and the stability constants of the various chiral supramolecular species in solution. [ABSTRACT FROM AUTHOR]

The hydrogen-evolving photocatalyst [(tbbpy)2Ru(tpphz)Pd(Cl)2]2+ (tbbpy=4,4′-di- tert-butyl-2,2′-bipyridine, tpphz=tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]phenazine) shows excitation-wavelength-dependent catalytic activity, which has been correlated to the localization of the initial excitation within the coordination sphere. In this contribution the excitation-wavelength dependence of the early excited-state relaxation and the occurrence of vibrational coherences are investigated by sub-20 fs transient absorption spectroscopy and DFT/TDDFT calculations. The comparison with the mononuclear precursor [(tbbpy)2Ru(tpphz)]2+ highlights the influence of the catalytic center on these ultrafast processes. Only in the presence of the second metal center, does the excitation of a 1MLCT state localized on the central part of the tpphz bridge lead to coherent wave-packet motion in the excited state. [ABSTRACT FROM AUTHOR]

Two classes of pincer-type PtII complexes containing tridentate N-donor ligands ( 1- 8) or C-deprotonated N^C^N ligands derived from 1,3-di(2-pyridyl)benzene ( 10- 13) and auxiliary N-heterocyclic carbene (NHC) ligand were synthesized. [Pt(trpy)(NHC)]2+ complexes 1- 5 display green phosphorescence in CH2Cl2 ( Φ: 1.1-5.3 %; τ: 0.3-1.0 μs) at room temperature. Moderate-to-intense emissions are observed for 1- 7 in glassy solutions at 77 K and for 1- 6 in the solid state. The [Pt(N^C^N)(NHC)]+ complexes 10- 13 display strong green phosphorescence with quantum yields up to 65 % in CHCl3. The reactions of 1 with a wide variety of anions were examined in various solvents. The tridentate N-donor ligand of 1 undergoes displacement reaction with CN− in protic solvents. Similar displacement of the N^C^N ligand by CN− has been observed for 10, leading to a luminescence 'switch-off' response. The water-soluble 7 containing anthracenyl-functionalized NHC ligand acts as a light 'switch-on' sensor for the detection of CN− ion with high selectivity. The in vitro cytotoxicity of the PtII complexes towards HeLa cells has been evaluated. Complex 12 showed high cytotoxicity with IC50 value of 0.46 μ M, whereas 1- 4 and 6- 8 are less cytotoxic. The cellular localization of the strongly luminescent complex 12 traced by using emission microscopy revealed that it mainly localizes in the cytoplasmic structures rather than in the nucleus. This complex can induce mitochondria dysfunction and subsequent cell death. [ABSTRACT FROM AUTHOR]

Fluorescence detection is the most effective tool for tracking gene delivery in living cells. To reduce photodamage and autofluorescence and to increase deep penetration into cells, choosing appropriate fluorophores that are capable of two-photon activation under irradiation in the NIR or IR regions is an effective approach. In this work, we have developed six tetranuclear ruthenium(II) complexes, GV1-6, and have studied their one- and two-photon luminescence properties. DNA interaction studies have demonstrated that GV2-6, bearing hydrophobic alkyl ether chains, show more efficient DNA condensing ability but lower DNA binding constants than GV1. However, the hydrophobic alkyl ether chains also enhance the DNA delivery ability of GV2-6 compared with that of GV1. More importantly, we have applied GV1-6 as non-viral gene vectors for tracking DNA delivery in living cells by one- and two-photon fluorescence microscopies. In two-photon microscopy, a high signal-to-noise contrast was achieved by irradiation with an 830 nm laser. This is the first example of the use of transition-metal complexes for two-photon luminescent tracking of the cellular pathways of gene delivery and as DNA carriers. Our work provides new insights into improving real-time tracking during gene delivery and transfection as well as important information for the design of multifunctional non-viral vectors. [ABSTRACT FROM AUTHOR]

Nature uses hydrogenase enzyme to catalyze proton reduction at pH 7 with overpotentials and catalytic efficiencies that rival platinum electrodes. Over the past several years, [FeFe]-hydrogenase ([FeFe]-H2ase) mimics have been demonstrated to be effective catalysts for light-driven H2 evolution. However, it remains a significant challenge to realize H2 production by such an artificial photosynthetic system in neutral aqueous solution. Herein, we report a new system for photocatalytic H2 evolution working in a broad pH range, especially under neutral conditions. This unique system is consisted of branched polyethylenimine (PEI)-grafted [FeFe]-H2ase mimic (PEI- g-Fe2S2), MPA-CdSe quantum dots (MPA=mercaptopropionic acid), and ascorbic acid (H2A) in water. Due to the secondary coordination sphere of PEI, which has high buffering capacity and stabilizing ability, the system is able to produce H2 under visible-light irradiation with turnover number of 10 600 based on the Fe2S2 active site in PEI- g-Fe2S2. The stability and activity are much better than that of the same system under acidic or basic conditions and they are, to the best of our knowledge, the highest known to date for photocatalytic H2 evolution from a [FeFe]-H2ase mimic in neutral aqueous solution. [ABSTRACT FROM AUTHOR]

The synthesis, photophysical and electrochemical properties as well as theoretical calculation studies of a newly designed triphenylamine derivative are described. This original compound displays one neutral form, three oxidized forms, and two protonated forms with distinct photophysical characteristics. The interplay of the emission with the protonation or the redox state (electrofluorochromism) has been explored and an on-off-on-off fluorescence switching was observed in the case of oxidation and an on-on-off fluorescence switching in the case of protonation. [ABSTRACT FROM AUTHOR]

In the present study, a biomimetic reaction center model, that is, a molecular triad consisting of a chlorin dimer and an azafulleroid, is synthesized and its photophysical properties are studied in comparison with the corresponding molecular dyad, which consists only of a chlorin monomer and an azafulleroid. As evidenced by 1H NMR, UV/Vis, and fluorescence spectroscopy, the chlorin dimer-azafulleroid folds in nonpolar media into a C2-symmetric geometry through hydrogen bonding, resulting in appreciable electronic interactions between the chlorins, whereas in polar media the two chlorins diverge from contact. Femtosecond transient absorption spectroscopy studies reveal longer charge-separated states for the chlorin dimer-azafulleroid; ≈1.6 ns in toluene, compared with the lifetime of ≈0.9 ns for the corresponding chlorin monomer-azafulleroid in toluene. In polar media, for example, benzonitrile, similar charge-separated states are observed, but the lifetimes are inevitably shorter: 65 and 73 ps for the dimeric and monomeric chlorin-azafulleroids, respectively. Nanosecond transient absorption and singlet oxygen phosphorescence studies corroborate that in toluene, the charge-separated state decays indirectly via the triplet excited state to the ground state, whereas in benzonitrile, direct recombination to the ground state is observed. Complementary DFT studies suggest two energy-minima conformations, that is, a folded chlorin dimer-azafulleroid, which is present in nonpolar media, and another conformation in polar media, in which the two hydrophobic chlorins wrap the azafulleroid. Inspection of the frontier molecular orbitals shows that in the folded conformation, the HOMO on each chlorin is equivalent and is shared owing to partial π-π overlap, resulting in delocalization of the conjugated π electrons, whereas the wrapped conformation lacks this stabilization. As such, the longer charge-separated lifetime for the dimer is rationalized by both the electron donor-acceptor separation distance and the stabilization of the radical cation through delocalization. The chlorin folding seems to change the photophysical properties in a manner similar to that observed in the chlorophyll dimer in natural photosynthetic reaction centers. [ABSTRACT FROM AUTHOR]

We demonstrate a new approach to manipulate the selective emission in mixed electrogenerated chemiluminescence (ECL) systems, where subtle changes in co-reactant properties are exploited to control the relative electrontransfer processes of excitation and quenching. Two closely related tertiary-amine co-reactants, tri-n-propylamine and N,N-diisopropylethylamine, generate remarkably different emission profiles: one provides distinct green and red ECL from [Ir(ppy)3] (ppy=2-phenylpyridinato-C2,N) and a [Ru(bpy)3]2+ (bpy=2,2'-bipyridine) derivative at different applied potentials, whereas the other generates both emissions simultaneously across a wide potential range. These phenomena can be rationalized through the relative exergonicities of electron-transfer quenching of the excited states, in conjunction with the change in concentration of the quenchers over the applied potential range. [ABSTRACT FROM AUTHOR]

Heteroleptic copper(I) complexes have been prepared from a macrocyclic ligand incorporating a 2,9-diphenyl- 1,10-phenanthroline subunit (M30) and two bis-phosphines, namely bis[(2-diphenylphosphino)phenyl] ether (POP) and 1,3-bis(diphenylphosphino)propane (dppp). In both cases, the diphenylphosphino moieties of the PP ligand are too bulky to pass through the 30-membered ring of M30 during the coordination process, hence the formation of C2v-symmetrical pseudo-rotaxanes is prevented. When POP is used, X-ray crystal structure analysis shows the formation of a highly distorted [Cu(M30)(POP)]+ complex in which the POP ligand is only partially threaded through the M30 unit. This compound is poorly stable as the CuI cation is not in a favorable coordination environment due to steric constraints. By contrast, in the case of dppp, the bis-phosphine ligand undergoes both steric and topological constraints and adopts a nonchelating coordination mode to generate [Cu2(M30)2(μ-dppp)](BF4)2. This compound exhibits metal-to-ligand charge transfer (MLCT) emission characterized by a very large Stokes' shift (≈200 nm) that is not attributed to a dramatic structural distortion between the ground and the emitting states but to very weak MLCT absorption transitions at longer wavelengths. Accordingly, [Cu2(M30)2(μ-dppp)](BF4)2 shows unusually high luminescence quantum yields for CuI complexes, both in solution and in the solid state (0.5 and 7%, respectively). [ABSTRACT FROM AUTHOR]

We have designed a new multichromophoric system based on a tetra(phenylthio)pyrene core appended with four terpyridine units. The system behaves as a molecular antenna that collects light with the peripheral units and funnels the energy to the very highly luminescent core. The addition of metals ions to the investigated system can not only switch the direction of the intramolecular energy transfer, but also control the formation of three-dimensional nanoscopic objects in a dual function. [ABSTRACT FROM AUTHOR]

Protoporphyrin IX-zinc oxide (PP-ZnO) nanohybrids have been synthesized for applications in photocatalytic devices. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and steady-state infrared, absorption, and emission spectroscopies have been used to analyze the structural details and optical properties of these nanohybrids. Time-resolved fluorescence and transient absorption techniques have been applied to study the ultrafast dynamic events that are key to photocatalytic activities. The photocatalytic efficiency under visible-light irradiation in the presence of naturally abundant iron(III) and copper(II) ions has been found to be significantly retarded in the former case, but enhanced in the latter case. More importantly, femtosecond (fs) transient absorption data have clearly demonstrated that the residence of photoexcited electrons from the sensitizer PP in the centrally located iron moiety hinders ground-state bleach recovery of the sensitizer, affecting the overall photocatalytic rate of the nanohybrid. The presence of copper(II) ions, on the other hand, offers additional stability against photobleaching and eventually enhances the efficiency of photocatalysis. In addition, we have also explored the role of UV light in the efficiency of photocatalysis and have rationalized our observations from femtosecond- to picosecond-resolved studies. [ABSTRACT FROM AUTHOR]

Rhenium triscarbonyl complexes fac-[Re(CO)3(N^N)] with appropriate ancillary N^N ligands are relevant for fluorescent bio-imaging. Recently, we have shown that [Re(CO)3] cores can also be efficiently mapped inside cells using their IR signature and that they can thus be used in a bimodal approach. To describe them we have coined the term SCoMPIs for single-core multimodal probes for imaging. In the context of the use of these SCoMPIs in bio-imaging, the questions of their cellular uptake and cytotoxicity are critical. We report here a series of compounds derived from the [Re(CO)3Cl(pyta)] core (pyta=4-(2-pyridyl)-1,2,3-triazole). The pyta ligand is of interest because it can be easily functionalized. Aliphatic side chains (C4, C8, and C12) were appended to this core. A correlative study involving IR and luminescence was performed to monitor and quantify their cellular internalization. We studied the relationship between lipophilicity (log P(o/w)), cytotoxicity (IC50), and cellular uptake, and we showed that both uptake and cytotoxicity increase with the length of the side chain, with a higher uptake for the C12 derivative. This study stresses the distinction that has to be made between apparent toxicity, determined as an incubation concentration IC50, and intrinsic toxicity. Indeed, the intrinsic toxicity of a compound can remain hidden if it is not cell permeable. Therefore it must be kept in mind that IC50 values are composite values, reflecting both cellular uptake and intrinsic toxicity. [ABSTRACT FROM AUTHOR]

The synthesis of a new class of robust squaraine dyes, colloquially named 1,2-hemisquarimines (1,2-HSQiMs), through the microwave-assisted condensation of aniline derivatives with the 1,2-squaraine core is reported. In CH3CN, 1,2-HSQiMs show a broad absorption band with a high extinction coefficient and a maximum at around λ=530 nm, as well as an emission band centered at about λ=574 nm, that are pH dependent. Protonation of the imine nitrogen causes a redshift of both absorption and emission maxima, with a concomitant increase in the lifetime of the emitting excited state. Encapsulation of the chromophore into a cucurbit[7]uril host revealed fluorescence enhancement and increased photostability in water. The redox characteristics of 1,2-HSQiMs indicate that charge injection into TiO2 is possible; this opens up promising perspectives for their use as photosensitizers for solar energy conversion. [ABSTRACT FROM AUTHOR]

The spectroscopic and photophysical properties of triarylborane derivatives were controlled by the nature of the triarylborane core (trixylyl- or trianthrylborane) and peripheral electron-donating groups ( N, N-diphenylamino or 9 H-carbazolyl groups). The triarylborane derivatives with and without the electron-donating groups showed intramolecular charge-transfer absorption/fluorescence transitions between the π orbital of the aryl group (π(aryl)) and the vacant p orbital on the boron atom (p(B), π(aryl)-p(B) CT), and the fluorescence color was tunable from blue to red by the combination of peripheral electron-donating groups and a triarylborane core. Detailed electrochemical, spectroscopic, and photophysical studies of the derivatives, including solvent dependences of the spectroscopic and photophysical properties, demonstrated that the HOMO and LUMO of each derivative were determined primarily by the nature of the peripheral electron-donating group and the triarylborane core, respectively. The effects of solvent polarity on the fluorescence quantum yield and lifetime of the derivatives were also tunable by the choice of the triarylborane core. [ABSTRACT FROM AUTHOR]

A series of triarylamine-containing tricarbonyl rhenium(I) complexes, [BrRe(CO)3(N^N)] (N^N=5,5′-bis( N, N-diaryl-4-[ethen-1-yl]-aniline)-2,2′-bipyridine), has been designed and synthesized by introducing a rhenium(I) metal center into a donor-π-acceptor-π-donor structure. All of the complexes showed an intense broad structureless emission band in dichloromethane at around 680-708 nm, which originated from an excited state of intraligand charge transfer (3ILCT) character from the triarylamine to the bipyridine moiety. Upon introduction of the bulky and electron-donating pentaphenylbenzene units attached to the aniline groups, the emission bands were found to be red shifted. The nanosecond transient absorption spectra of two selected complexes were studied, which were suggestive of the formation of an initial charge-separated state. Computational studies have been performed to provide further insight into the origin of the absorption and emission. One of the rhenium(I) complexes has been utilized in the fabrication of organic light-emitting diodes (OLEDs), representing the first example of the realization of deep red to near-infrared rhenium(I)-based OLEDs with an emission extending up to 800 nm. [ABSTRACT FROM AUTHOR]

Homodinuclear lanthanide complexes (Ln=La, Eu, Gd, Tb, Yb and Lu) derived from a bis-macrocyclic ligand featuring two 2,2′,2′′-(1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid chelating sites linked by a 2,6-bis(pyrazol-1-yl)pyridine spacer (H2L3) were prepared and characterized. Luminescence lifetime measurements recorded on solutions of the EuIII and TbIII complexes indicate the presence of one inner-sphere water molecule coordinated to each metal ion in these complexes. The overall luminescence quantum yields were determined ( ϕ [ABSTRACT FROM AUTHOR]

A new class of luminescent alkynylplatinum(II) complexes with a tridentate pyridine-based N-heterocyclic carbene (2,6-bis(1-butylimidazol-2-ylidenyl)pyridine) ligand, [PtII(C^N^C)(CCR)][PF6], and their chloroplatinum(II) precursor complex, [PtII(C^N^C)Cl][PF6], have been synthesized and characterized. One of the alkynylplatinum(II) complexes has also been structurally characterized by X-ray crystallography. The electrochemistry, electronic absorption and luminescence properties of the complexes have been studied. Nanosecond transient absorption (TA) spectroscopy has also been performed to probe the nature of the excited state. The origin of the absorption and emission properties has been supported by computational studies. [ABSTRACT FROM AUTHOR]

Two‐in‐one fluorescent compounds: Blending the strong emitter, diquinaldinato aluminum, and the good electron transporter, tetraphenyl silole, resulted in highly fluorescent compounds that are promising candidates for light‐emitting devices without the need of dopants (see figure). [ABSTRACT FROM AUTHOR]

To examine the impact of metal moieties that have different triplet energies on the photoisomerization of B(ppy)Mes2 compounds (ppy=2-phenyl pyridine, Mes=mesityl), three metal-functionalized B(ppy)Mes2 compounds, Re-B, Au-B, and Pt-B, have been synthesized and fully characterized. The metal moieties in these three compounds are Re(CO)3( tert-Bu2bpy)(CC), Au(PPh3)(CC), and trans-Pt(PPh3)2(CC)2, respectively, which are connected to the ppy chelate through the alkyne linker. Our investigation has established that the ReI unit completely quenches the photoisomerization of the boron unit because of a low-lying intraligand charge transfer/MLCT triplet state. The AuI unit, albeit with a triplet energy that is much higher than that of B(ppy)Mes2, upon conjugation with the ppy chelate unit, substantially increases the contribution of the π→π* transition, localized on the conjugated chelate backbone in the lowest triplet state, thereby leading to a decrease in the photoisomerization quantum efficiency (QE) of the boron chromophore when excited at 365 nm. At higher excitation energies, the photoisomerization QE of Au-B is comparable to that of the silyl-alkyne-functionalized B(ppy)Mes2 ( TIPS-B), which was attributable to a triplet-state-sensitization effect by the AuI unit. The PtII unit links two B(ppy)Mes2 together in Pt-B, thereby extending the π-conjugation through both chelate backbones and leading to a very low QE of the photoisomerization. In addition, only one boron unit in Pt-B undergoes photoisomerization. The isomerization of the second boron unit is quenched by an intramolecular energy transfer of the excitation energy to the low-energy absorption band of the isomerized boron unit. TD-DFT computations and spectroscopic studies of the three metal-containing boron compounds confirm that the photoisomerization of the B(ppy)Mes2 chromophore proceeds through a triplet photoactive state and that metal units with suitable triplet energies can be used to tune this system. [ABSTRACT FROM AUTHOR]

A series of novel CdII complexes based on α,β-unsubstituted dipyrrin ligands (dpm) has been prepared and characterised both in solution and in the solid state. These compounds are of the [Cd(dpm)2] type, with the coordination sphere of the metal centre occupied by two dpm chelates. Interestingly, in contrast to what has been reported for the ZnII analogues, in the presence of a pyridyl- or imidazolyl-appended dpm ligand, the coordination number of the CdII cation can be increased to six, leading to an octahedral coordination sphere. As a consequence, the formation of 1-, 2-, and 3D coordination polymers by self-assembly is observed. Photophysical investigations of the discrete complexes and self-assembled networks have demonstrated that both types of compounds are luminescent in the solid state. [ABSTRACT FROM AUTHOR]

Two-photon microscopy (TPM) has become an indispensable tool in the study of biology and medicine due to the capability of this method for molecular imaging deep inside intact tissues. For the maximum utilization of TPM, a variety of two-photon (TP) probes for specific applications are needed. In this article, we report a small-molecule TP probe (ANO1) for nitric oxide (NO) that shows a rapid and specific NO response, a 68-fold fluorescence enhancement in response to NO, and a maximum TP-action cross-section of 170 GM (GM: 10−50 cm4 photon−1) upon reaction with excess NO. This probe can be easily loaded into cells and tissues and can real-time monitor NO in living tissues at 100-180 μm depth for longer than 1200 s through the use of TPM, with minimum interference from other biologically relevant species. [ABSTRACT FROM AUTHOR]

The synthesis of a geometrically constrained and near-planar hexacyclic acridinium cyanine dye 9 is reported. When compared to its unlocked and non-fluorescent monomethine cyanine dye analogue 3, this photostable dye emits in the green area of the spectrum with a remarkable quantum yield close to unity in organic solvents and above 0.5 in water. A detailed steady-state and time-resolved spectroscopic study revealed that dye 9 forms emissive aggregates in water, which are responsible for a red-shifted and broadened emission band and longer emission lifetime, τ≈33 compared to 6.5-7.0 ns for the monomeric dye. Dye 9 also binds strongly to DNA (both duplex and quadruplex) in its monomeric form and is very efficiently taken up by cells, in which it accumulates primarily into the nucleus. [ABSTRACT FROM AUTHOR]

A series of platinum(II) diimine complexes with different substituents on fluorenyl acetylide ligands ( 1 a- 1 e) were synthesized and characterized. The influence of the auxiliary substituent on the photophysics of these complexes has been systematically investigated spectroscopically and theoretically (using density functional theory (DFT) methods). All complexes exhibit ligand-centered 1π,π* transitions in the UV and blue spectral region, and broad, structureless 1MLCT/1LLCT ( 1 a, 1 b, 1 d and 1 e) or 1MLCT/1LLCT/1π,π* ( 1 c) absorption bands in the visible region. All complexes are emissive in solution at room temperature, with the emitting state is tentatively assigned to mixed 3MLCT/3π,π* states. The degree of 3π,π* and 3MLCT mixing varies with different substituents and solvent polarities. Complexes 1 a- 1 e exhibit relatively strong singlet and triplet transient absorption from 450 to 800 nm, at which point reverse saturable absorption (RSA) could occur. Nonlinear transmission experiments at 532 nm by using nanosecond laser pulses demonstrate that 1 a- 1 e are strong reverse saturable absorbers and could potentially be used as broadband nonlinear absorbing materials. [ABSTRACT FROM AUTHOR]