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Herein we report the synthesis, characterization, photophysical and theoretical study of the luminescent dyad Ir‐RhB containing two emissive centers: The first fluorescent (RhB=rhodamine B) and the second phosphorescent (Ir=orthometalated iridium complex), bound with an aliphatic bridge. These nearly independent chromophores have triplet excited states which are very close in terms of energy, allowing for reversible energy transfer between them. The observed transient absorption spectra and their time dependent variations were interpreted in terms of a relatively simple kinetic model, where selective excitation of the iridium‐based chromophore affords the corresponding emissive triplet state, followed by its equilibration with the rhodamine based triplet state and simultaneous emissive relaxation to the dyad ground state. This model allows for analytical solution to give key characteristics of the dyad excited‐state dynamics, including the energy gap between these triplets (ΔE=0.017 eV) and the rate constant of energy transfer (k(Ir‐RhB)=6.0 ⋅ 108 s−1). These data were also verified by quantum chemical DFT and TD‐DFT calculations. [ABSTRACT FROM AUTHOR]

Abstract: A series of gold(I) iodide complexes 1–11 have been prepared from di‐, tri‐, and tetraphosphane ligands. Crystallographic studies reveal that the di‐ (1–7) and tetrametallic (11) compounds feature linearly coordinated gold(I) ions with short aurophilic contacts. Their luminescence behavior is determined by the combined influence of the phosphane properties, metal–metal interaction, and intermolecular lattice‐defined interactions. The proposed variable contribution of 3(X+M)‐centered (X=halogen; M=metal) and 3XLCT (halogen to ligand charge transfer) electronic transitions into the lowest lying excited state, which is influenced by supramolecular packing, is presumably responsible for the alteration of room‐temperature emission color from green (λ=545 nm, for 11) to near‐IR (λ=698 nm, for 2). Dinuclear compounds 6 and 7 exhibit distinct luminescence thermochromism with a blueshift up to 5750 cm−1 upon cooling. Such dramatic change of emission energy is assigned to the presence of two coupled triplet excited states of 3ππ* and 3(X+M)C/3XLCT nature, the presence of which depends on both molecular structure and the crystal lattice arrangement. [ABSTRACT FROM AUTHOR]

Abstract: The series of cyanide‐bridged coordination polymers [(P2)CuCN]n (1), [(P2)Cu{M(CN)2}]n (M=Cu 3, Ag 4, Au 5) and molecular tetrametallic clusters [{(P4)MM'(CN)}2]2+ (MM′=Cu26, Ag27, AgCu 8, AuCu 9, AuAg 10) were obtained using the bidentate P2 and tetradentate P4 phosphane ligands (P2=1,2‐bis(diphenylphosphino)benzene; P4=tris(2‐diphenylphosphinophenyl)phosphane). All title complexes were crystallographically characterized to reveal a zig‐zag chain arrangement for 1 and 3–5, whereas 6–10 possess metallocyclic frameworks with different degree of metal‐metal bonding. The d10–d10 interactions were evaluated by the quantum theory of atoms in molecules (QTAIM) computational approach. The photophysical properties of 1–10 were investigated in the solid state and supported by theoretical analysis. The emission of compounds 1 and 3–5, dominated by metal‐to‐ligand charge transfer (MLCT) transitions located within {CuP2} motifs, is compatible with thermally activated delayed fluorescence (TADF) behaviour and a small energy gap between the T1 and S1 excited states. The luminescence characteristics of 6–10 are strongly dependent on the composition of the metal core; the emission band maxima vary in the range 484–650 nm with quantum efficiency reaching 0.56 (6). The origin of the emission for 6–8 and 10 at room temperature is assigned to delayed fluorescence. AuCu cluster 9, however, exhibits only phosphorescence that corresponds to theoretically predicted large value ΔE(S1−T1). DFT simulation highlights a crucial impact of metallophilic bonding on the nature and energy of the observed emission, the effect being greatly enhanced in the excited state. [ABSTRACT FROM AUTHOR]

The bifunctional aminopyridine ligands H2N-(CH2) n-4-C5H4N ( n=0, L1; 1, L2; 2, L3) have been utilized for the preparation of the rhenium complexes [Re(phen)(CO)3( L1- L3)]+ ( 1- 3; phen=phenanthroline). Complexes 2 and 3 with NH2-coordinated L2 and L3, respectively, were coupled with cycloplatinated motifs {Pt(ppy)Cl} and {Pt(dpyb)}+ (ppy=2-phenylpyridine, dpyb=dipyridylbenzene) to give the bimetallic species [Re(phen)(CO)3(μ- L2/ L3)Pt(ppy)Cl]+ ( 4, 6) and [Re(phen)(CO)3(μ- L2/ L3)Pt(dpyb)]2+ ( 5, 7). In solution, complexes 4 and 6 show 3MLCT {Re}-based emission at 298 K, which changes to the 3IL(ppy) state at 77 K. The photophysical properties of compounds 5 and 7 display a pronounced concentration dependence, presumably due to the formation of bimolecular aggregates. Analysis of the spectroscopic data, combined with TD-DFT simulations, suggest that unconventional heteroleptic {Re(phen)}⋅⋅⋅{Pt(dpyb)} π-π stacking operates as the driving force for ground-state association. The latter, together with intra- and intermolecular energy-transfer processes, determines the appearance of multiple emission bands and results in nonlinear relaxation kinetics of the excited states. [ABSTRACT FROM AUTHOR]

The Schiff base NNO ligand 1‐(furan‐2‐yl)‐N‐[(2‐methyl‐1H‐imidazol‐4‐yl)methylene]methanamine was synthesized and structurally characterized by XRD crystallography, mass spectrometry, and NMR spectroscopy. Quantum‐chemical calculations revealed conformational flexibility of the ligand backbone to give two different conformations with nearly equal ground‐state energies. The orientation of two nitrogen atoms and the oxygen atom in one conformation is a good fit for the NNO tridentate coordination mode, whereas the other would allow the NN coordination mode only. Two lanthanide complexes [Ln(tta)3(NNO)] (Ln = EuIII and LuIII; tta = thenoyltrifluoroacetone) were prepared and studied spectroscopically. The structures of the complexes were optimized by the DFT approach. The NNO ligand in the Eu complex displays tridentate NNO coordination, whereas the ligand is only NN‐coordinated in the Lu complex. The Eu complex shows bright red metal‐centered phosphorescence under excitation into the ligand (π–π*) absorption bands with a quantum yield of ca. 80 % and a lifetime of 580 μs. A mechanism for energy transfer between the ligands and metal centers was suggested and confirmed by DFT and time‐dependent DFT (TDDFT) studies. An organic light‐emitting diode (OLED) device based on the Eu complex incorporated into a poly(9‐vinylcarbazole) (PVK) matrix was prepared. A study of the characteristics of the device revealed electrochromism of the system owing to variations in the efficacy of metal‐centered and matrix emission at different strengths of applied electric field.Neutral EuIII and LuIII diketonate complexes with a Schiff base NNO ligand are studied spectroscopically. The Eu complex shows red metal‐centered phosphorescence with a quantum yield of ca. 80 %. An organic light‐emitting device (OLED) with the Eu complex in a poly(9‐vinylcarbazole) (PVK) matrix reveals electrochromism owing to variations in the efficacy of the metal‐centered and matrix emission. [ABSTRACT FROM AUTHOR]

This article develops a damage model for unfilled crosslinked rubbers based on the concept of scission of polymer chains. The model is built up on the well-known Gent elastic potential complemented by a kinetic equation describing effects of polymer chain scission. The macroscopic parameters in the damage model are evaluated through the parameters for undamaged elastomer. Qualitative analysis of changing molecular parameters of rubbers under scission of polymer chains resulted in easy scaling modeling the dependences of these parameters on the damage factor. It makes possible to predict the rubber failure in molecular terms as mechanical devulcanization. The model was tested in tensile quasistatic experiments with both the monotonous loading and repeated loading-unloading. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Reactions of the [(tppm)Au3Cl3] [tppm = tris(diphenylphosphanyl)methane] precursor and CuI ions with a stoichiometric amount of the corresponding linear mono- [HC2(C6H4) nC6H5; n = 1, 2] and diacetylenes [HC2(C6H4) nC2H; n = 1-3] that contain extended polyaryl moieties afford a series of luminescent heterometallic complexes with a common structural motif based on the {(AuC2)3Cu} cluster core. The complexes obtained were characterized by using X-ray crystallography and NMR spectroscopy. All compounds studied display dual singlet and triplet luminescence, the former component of which can be completely suppressed in concentrated solution by a self-absorption phenomenon. The results of the photophysical measurements together with the quantum chemical calculations (PBE0-DFT level of theory) indicate that singlet emission originates mainly from copper-perturbed intraligand transitions, whereas the phosphorescence can be assigned to the {(AuC2)3Cu} core-centered transitions. Due to the low contribution of the gold atoms to the orbitals responsible for the singlet and triplet emission, the emissive excited states are very weakly coupled, thereby resulting in a negligible energy transfer between these excited states. [ABSTRACT FROM AUTHOR]