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Carl Michael Weisshuhn - One of the best experts on this subject based on the ideXlab platform.

  • Polymerizable mesoionic 4,6-dioxo-1,3-Diazines, 1. Synthesis and photochemical behavior of polystyrenes with mesoionic 4,6-dioxo-1,3-Diazines as pendant groups
    Macromolecular Chemistry and Physics, 1994
    Co-Authors: Helmut Ritter, Rolf Sperber, Carl Michael Weisshuhn
    Abstract:

    Mesoionic 5-alkyl-4,6-dioxo-1,3-diphenyl-2-(3-vinylbenzylthio)-1,3-Diazine (6) was prepared by condensation of alkylmalonic acid (5) with 1,3-diphenyl-2-(3-vinylbenzyl)isothiourea (4) by use of dicyclohexylcarbodiimide (DCC). Homopolymerization of 6 led to new polystyrene derivatives (7) with mesoionic 4,6-dioxo-1,3-Diazines as pendant groups. UV irradiation of 7 yielded polystyrene derivatives with bis(β-lactam) moieties as pendant groups (8). The change of some physical properties during the irradiation is discussed. 5-Heptyl-4,6-dioxo-1,3-diphenyl-2-(3-methylbenzylthio)-1,3-Diazine (11) and 4-heptyl-1-(3-methylbenzylthio)-3,5-dioxo-2,6-diphenyl-2,6-diazabicyclo[2.2.0]hexane (12) as low-molecular-weight model compounds were synthesized for structural analysis.

Luisa De Cola - One of the best experts on this subject based on the ideXlab platform.

  • Luminescent dinuclear rhenium(I) complexes containing bridging 1,2-Diazine ligands: Photophysical properties and application
    Coordination Chemistry Reviews, 2012
    Co-Authors: Monica Panigati, Matteo Mauro, Daniela Donghi, Pierluigi Mercandelli, Patrizia Romana Mussini, Luisa De Cola, Giuseppe Alfonso
    Abstract:

    Abstract In this contribution we provide an overview of the preparation and of the properties of different classes of luminescent dinuclear tricarbonyl rhenium(I) complexes of general formula [Re 2 (μ-X) 2 (CO) 6 (μ-1,2-Diazine)] (X = halide, hydride, alkoxide, and thiolate). Their electrochemical and photophysical properties in solution are presented, as well as combined density functional (DFT) and time-dependent density functional (TDDFT) studies of their geometry, relative stability and electronic structure. The relationships between the structure and the emission properties of the complexes are discussed in detail, showing a modulation effect of the bridging ancillary ligands as well as of the Diazine substituents on energy, lifetime and quantum yield of the emission. Photoluminescent quantum yields ( Φ ) up to 0.53 have been measured in fluid solution for the dichloro complexes containing Diazines bearing alkyl groups in both the β positions, designed to optimize all the parameters responsible for the radiative decay. The photophysical properties in the solid state are also briefly presented, showing in some cases an increase of the emission intensity, discussed in terms of restriction of intramolecular roto-vibrational motions. These properties, together with their good processability and high stability, allowed the successful use of some of these complexes as a phosphorescent dopant in OLEDs. The good performances of OLED devices prepared both by solution- and vacuum-processing are reported. The preliminary work exploring the potential of these complexes as luminescent labels for bioimaging is also presented.

  • Luminescent dinuclear rhenium(I) complexes contain ing bridging 1,2-Diazine ligands : photophysical properties and application
    'Elsevier BV', 2012
    Co-Authors: Monica Panigati, Daniela Donghi, Pierluigi Mercandelli, Patrizia Romana Mussini, Luisa De Cola, M. Mauro, G. D&#8217
    Abstract:

    In this contribution we provide an overview of the preparation and of the properties of different classes of luminescentdinuclear tricarbonyl rhenium(I) complexes of general formula [Re2(\u3bc-X)2(CO)6(\u3bc-1,2-Diazine)] (X = halide, hydride, alkoxide, and thiolate). Their electrochemical and photophysical properties in solution are presented, as well as combined density functional (DFT) and time-dependent density functional (TDDFT) studies of their geometry, relative stability and electronic structure. The relationships between the structure and the emission properties of the complexes are discussed in detail, showing a modulation effect of the bridging ancillary ligands as well as of the Diazine substituents on energy, lifetime and quantum yield of the emission. Photoluminescent quantum yields (\u3a6) up to 0.53 have been measured in fluid solution for the dichloro complexes containing Diazines bearing alkyl groups in both the \u3b2 positions, designed to optimize all the parameters responsible for the radiative decay. The photophysical properties in the solid state are also briefly presented, showing in some cases an increase of the emission intensity, discussed in terms of restriction of intramolecular roto-vibrational motions. These properties, together with their good processability and high stability, allowed the successful use of some of these complexes as a phosphorescent dopant in OLEDs. The good performances of OLED devices prepared both by solution- and vacuum-processing are reported. The preliminary work exploring the potential of these complexes as luminescent labels for bioimaging is also presented

  • Dinuclear rhenium complexes highly luminescent in solid state
    2010
    Co-Authors: Quartapelle E. Procopio, Daniela Donghi, Chen-han Chien, Pierluigi Mercandelli, Luisa De Cola, M. Mauro, G. D&#8217
    Abstract:

    The interest for luminescent materials able to efficiently emit in solid state is continuously growing, because in most applications the dyes are used as solid film. Concentration-quenching effects, affecting both organic and organometallic emitters [1-2] usually decrease PLQY in solid state. We present here a series of dinuclear Re(I) complexes whose emission is higher in solid state than in solution, and strongly depends on the nature of the halide ancillary ligand. These complexes belong to the family of neutral tricarbonyl Re(I) complexes with general formula [Re2(CO)6(\uf06d-1,2-Diazine)(\uf06d-X)2], where X could be halogen or hydride [3]. Some of them have recently gained interest for their intense yellow/green emission, occurring from triplet metal-to-ligand charge transfer (3MLCT) states [4], showing a modulation effect of the Diazine substituents on wavelengths, lifetimes and quantum yields of the emission. Photoluminescent quantum yield (PLQY) up to 0.53 have been measured for the di-chloro complexes containing Diazines bearing alkyl groups in both the \uf062 positions [5]. These properties allowed their successful use as phosphorescent dopants in organic light emitting devices (OLEDs) [5]. The influence of the halide ancillary ligand on the photophysical properties has been previously discussed in solution [2, 4]. Differently from the di-chloro derivative 1, the analogous di-bromo and di-iodo derivatives 2 and 3 are almost no emissive. We have now found an opposite behaviour in solid state. In fact all the complexes are very brilliant, showing intense yellow-orange emission whose maximum shifts to higher energy on going from 1 to 3 (from 560 nm for 1 and 2 to 548 nm for 3) with PLQY relatively low for 1 and higher for 2 and 3 (up to 0.50 for complex 2). This very high Aggregation Induced Emission (AIE) [6] will be discussed in terms of the restriction of the intramolecular roto-vibrational motions of the \u201cRe2(CO)6(\uf06d-X)2\u201d scaffold imposed by the rigid environment, as evidenced by the strong decrease of the knr. Moreover a parallel increase of kr is noticed, which clearly shows the influence of the halides on determining not only the energy of the excited state, but also the nature of the lowest (emitting) state [7]

  • Highly Emitting Neutral Dinuclear Rhenium Complexes as Phosphorescent Dopants for Electroluminescent Devices
    Advanced Functional Materials, 2009
    Co-Authors: Matteo Mauro, Elsa Quartapelle Procopio, Monica Panigati, Daniela Donghi, Chen-han Chien, Pierluigi Mercandelli, Patrizia Romana Mussini, Giuseppe Alfonso, Luisa De Cola
    Abstract:

    A series of neutral, dinuclear, luminescent rhenium(I) complexes suitable for phosphorescent organic light emitting devices (OLEDs) is reported. These compounds, of general formula [Re2(m-Cl)2(CO)6(m-1,2-Diazine)], contain Diazines bearing alkyl groups in one or in both the b positions. Their electrochemical and photophysical properties are presented, as well as a combined density functional and time-dependent density functional study of their geometry, relative stability and electronic structure. The complexes show intense green/yellow emissions in toluene solution and in the solid state and some of the complexes possess high emission quantum yields (f=0.18–0.22 for the derivatives with disubstituted Diazines). In butyronitrile glass, at 77K, due to the charge transfer character of the lowest (emitting) excited state, strong blue shift of the emission is observed, accompanied by a strong increase in the lifetime values. The highest-performing emitting complex, containing cyclopentapyridazine as ligand, is tested in a polymer-based lightemitting device, with poly(9-vinylcarbazole) as matrix, as well as in a device obtained by vacuum sublimation of the complex in the 2,7bis(diphenylphosphine oxide)-9-(9-phenylcarbazol-3-yl)-9-phenylfluorene (PCF) matrix. This represents the first example of devices obtained with a rhenium complex which can be sublimed and is solution processable. Furthermore, the emission is the bluest ever reported for electrogenerated luminescence for rhenium complexes.

  • Photoluminescent and crystal structure properties of the yellow and orange forms of [Re2(m-Cl)2(CO)6(m- 4,5-trimethyl-silyl-pyridazine]
    2009
    Co-Authors: Quartapelle E. Procopio, Monica Panigati, Daniela Donghi, Pierluigi Mercandelli, M. Mauro, G. D&#8217, A.a.d. Sironi, Luisa De Cola
    Abstract:

    A series of neutral, dinuclear, luminescent rhenium(I) complexes suitable for phosphorescent organic light emitting devices (OLEDs) has been recently reported1,2. These compounds, of general formula [Re2(\u3bc-Cl)2(CO)6(\u3bc-1,2-Diazine)], contain Diazines bearing alkyl groups in one or in both the b positions. The complexes show intense green/yellow emissions in toluene solution and in the solid state and some of the complexes possess, in solution, high emission quantum yields (F 0.18-0.22 for the derivatives with disubstituted Diazines). The excited state responsible for this emission can be confidentially described as a triplet metal-to-ligand charge transfer (3MLCT) level3. Following the DFT computational suggestions we have now synthetized a new complex of this family using the 4,5-bis(trimetylsilyl)-1,2-Diazine ligand namely [Re2(m-Cl)2(CO)6(m- 4,5-trimethyl-silyl-pyridazine] (1, see Scheme). This complex has been completely carachterized in solution and it shows an emission maximum batochromically shifted respect to those of the analogous Re(I) compounds with alkyl-substituted Diazine, with a lower quantum yield. Slow evaporation at room temperature of a CH2Cl2 solution containing (1) induces the concomitant formation of orange and yellow single crystals (Figure 1, top). X-ray crystal structure determinations performed at room temperature as well as at 100 K, show that they are two different polymorphs of the same compound. The emission spectra recorded on crystalline samples of the two polymorph (Figure 1, bottom) are hypsochromically shifted respect to the solution one and present higher quantum yields (lem = 537 nm and F = 0.30 for the yellow phase, lem = 575 nm and F = 0.50, for the orange one). References (1) Mauro, M, Quartapelle Procopio, E., Sun,Y., Chien, C-H., Donghi, D., Panicati, M., Mercandelli, P., Mussini, P., D\u2019Alfonso, G., De Cola, L. Adv. Func. Mat. 2009, in press (2) Donghi, D., D\u2019Alfonso, G., Mauro, M, Panigati, M., Mercandelli, P., Sironi, A., Mussini, P., D\u2019Alfonso, L., Inorg. Chem. 2008, 47, 4243. (3) Wrighton, M., Morse, D. L., J. Am. Chem. Soc., 1974, 96, 998