Because of its ability to form stable complexes with a wide variety of metal ions, cyclam (1,4,8,11-tetraazacyclotetradecane) is one of the most studied ligands in coordination chemistry. ...Functionalizing the cyclam unit with photoactive dendrons open a door to construct giant homo- and heteroleptic metal complexes that display interesting spectroscopic properties, particularly as far as luminescence is concerned. Light is a tool both to study metal coordination processes, and to act as input or output in order to achieve the desired function.
This paper reviews some results obtained with metal complexes of cyclam-based dendrimers capable of acting as: (i) sensor, (ii) logic gates, and (iii) molecular antennae.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A strongly photoreducing ruthenium complex has been used to regenerate nicotinamide cofactor with only visible light and
l
-cysteine. The photoinduced processes have been deeply characterized, and ...the emission of NADH has been employed for the assessment of selectivity towards the enzymatically active photoregenerated cofactor.
An aged Ru complex has been successfully employed for the photochemical monoreduction of NAD
+
achieving mediator-free NADH formation with the only aid of
l
-cysteine and visible light.
A dendrimer with a Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) complex as a core and four diphenylanthracene units at the periphery was prepared from a scaffold based on a bipyridyl ligand bearing four ...terminal alkyne groups. Upon green light excitation, the dendrimer shows blue luminescence even in a rigid matrix at 77 K thanks to the dendritic multichromophoric structure.
Hexakis(phenylthio)benzene compounds carrying six carboxylic acid groups at their periphery combine aggregation-induced phosphorescence, water-solubility and metal-binding properties: the para-isomer ...is a selective and sensitive turn-on phosphorescent sensor of Pb2+ ions in water.
Hexakis(phenylthio)benzene compounds carrying six carboxylic acid groups at their periphery combine aggregation-induced phosphorescence, water-solubility and metal-binding properties: the
para
...-isomer is a selective and sensitive turn-on phosphorescent sensor of Pb
2+
ions in water.
Persulfurated asterisks functionalized with six carboxylic groups form a strongly green phosphorescent coordination polymer upon addition of Pb
2+
ions in aqueous solution. The self-assembly process is selective and reversible, enabling Pb
2+
sensing with a detection limit of 6.0 × 10
−7
M.
Tetraphenylmethane appended with four pyridylpyridinium units works as a scaffold to self‐assemble four ruthenium porphyrins in a tetrahedral shape‐persistent giant architecture. The resulting ...supramolecular structure has been characterised in the solid state by X‐ray single crystal analysis and in solution by various techniques. Multinuclear NMR spectroscopy confirms the 1 : 4 stoichiometry with the formation of a highly symmetric structure. The self‐assembly process can be monitored by changes of the redox potentials, as well as by modifications in the visible absorption spectrum of the ruthenium porphyrin and by a complete quenching of both the bright fluorescence of the tetracationic scaffold and the weak phosphorescence of the ruthenium porphyrin. An ultrafast photoinduced electron transfer is responsible for this quenching process. The lifetime of the resulting charge separated state (800 ps) is about four times longer in the giant supramolecular structure compared to the model 1 : 1 complex formed by the ruthenium porphyrin and a single pyridylpyridinium unit. Electron delocalization over the tetrameric pyridinium structure is likely to be responsible for this effect.
Giant multichromophore: A tetrahedral shape‐persistent supramolecular structure has been fully characterised in the solid state (by X‐ray diffraction) and in solution (by NMR, electrochemical and photophysical analysis). Excitation of either the scaffold (blue in the image) or the peripheral ruthenium porphyrins results in an ultrafast photoinduced electron transfer from the ruthenium porphyrins to the scaffold.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A series of functionalized persulfurated benzene molecules were synthesized. Their photophysical properties and crystal structures were analyzed. All compounds are non-emitting in solution at room ...temperature, but in a sharp contrast, quantum yields can be very high (up to 100%) in the solid state at 298 K or in a rigid matrix at low temperatures. This is a consequence of a decrease of intramolecular rotations and motions, but conformational and rotamer issues along with substituent effects might also play a role. These compounds are among the rare examples of highly phosphorescent organic materials, due to a Crystallization Induced Phosphorescence or to an Aggregation Induced Phosphorescence. Compound 1 is among the most phosphorescent solid known to date. They thus represent an alternative to heavy metal ion-based triplet emitters in solid state.
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•A family of persulfurated molecular asterisks was synthesized and fully characterized.•They display very intense phosphorescence in the solid state and in a rigid matrix.•X-ray crystal structures were analyzed and compared to the emission properties.•Phosphorescent nanoparticles were obtained by a reprecipitation method.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The photosensitivity of metal complexes has been known for a long time. Early studies on ligand photosubstitution and photoredox decomposition reactions of metal complexes of simple inorganic ligands ...(e.g. NH
3, CN
−) have been followed by accurate investigations on the photophysical behavior (luminescence quantum yields and lifetimes) and on the use of metal complexes in bimolecular processes (energy and electron transfer). A large number of complexes, stable towards photodecomposition, but capable of undergoing excited state redox processes, have been used for interconverting light and chemical energy. More recently, combination of supramolecular chemistry and photochemistry has led to the design and construction of multicomponent systems capable of performing light induced functions. In this field, luminescent and/or photoredox reactive metal complexes are presently used as essential components for a bottom-up approach to the construction of molecular devices and machines. Examples of molecular devices for processing light signals and of molecular machines powered by light energy, based on coordination compounds, are illustrated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The Front Cover shows a Dream Wedding! Bismuth and photoredox catalysis get married in this photoredox allylation reaction of aldehydes in aqueous solvent. The green reaction conditions (organic ...photoredox catalyst, available and not toxic metal, aqueous solvent) employed and the broad scope open new perspectives in the field of photoredox radical to polar cross over reactions. The profile of a well know Italian town on water is in the skyline. Where celebrate a better wedding? More information can be found in the Communication by G. Cozzi et al.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Pyrene‐based materials have gained considerable attention as stimuli‐responsive chemical sensors. We designed a polysulfurated arene system based on a tetra(phenylthio)pyrene core decorated with four ...carboxylic acid units. Three different regioisomers, ortho, meta and para were studied in organic and aqueous solution. These systems are soluble in water at pH≥8 due to the deprotonation of carboxylic acids. The addition of metal ions cannot only quench the fluorescence of the central pyrene core, but also control the formation of three‐dimensional nanoscopic objects in a dual mode function. Several divalent metal ions were tested and compared. Addition of ethylenediaminetetraacetic acid (EDTA) disassembles the non‐emissive supramolecular system and restores the initial fluorescence of the pyrene core.
Complexation power: Three novel regioisomers of a tetrasulfurated pyrene with four carboxylic acids (ortho, meta, para) were designed to complex divalent metal ions and to generate supramolecular polymers in aqueous solution. Depending on the presence of metal ions, the initial fluorescence of the pristine molecule is quenched, while generating supramolecular structures, leading to a dual mode sensor based on changes in aggregation and emission.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
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