The rigid [Cu(dmp)( phanephos)] + complex displays a high luminescence quantum yield of 80% at ambient temperature. In contrast to the long-lived phosphorescence of 240 µs at T < 120 K with a radiative rate of k r = 3 × 10 3 s −1 , the ambient-temperature emission represents a thermally activated delayed fluorescence (DF) with a decay time of only 14 μs and a radiative rate of k r (DF) = 6 × 10 4 s −1 . Evidence for the involvement of the excited singlet state in the emission process is presented. This material has high potential to be applied in efficient OLEDs taking advantage of the singlet harvesting mechanism.In the past decade, substantial investigations were carried out to develop novel materials for organic light emitting diodes (OLEDs), 1 in particular, to increase the device efficiency. In this respect, luminescent materials and excitation mechanisms play a crucial role. A breakthrough was reached by applying organometallic complexes based on the 3rd-row transition metals iridium and platinum. 2-6 These substances frequently display high phosphorescence quantum yields approaching even 100% and short emission decay times of a few μs. 7 Of special importance is the fact that by an electroluminescent excitation all triplet and singlet excitons formed in the emissive layer of an OLED can be utilized for light generation, whereby the emission stems from the lowest triplet state. This mechanism, representing the triplet harvesting effect, 8,9 is based on the properties of the organometallic compounds. It allows one to achieve much higher OLED efficiencies than obtainable with typical organic fluorescent (singlet) emitters by which only 25% of the total number of excitons can be exploited. However, the triplet emitters are based on high-cost platinum group metals. Therefore, alternative materials, such as Cu(I) complexes, 5,6,10-14 came into the focus of research. At first sight, Cu(I) complexes seem to exhibit substantial problems with regard to OLED applications: (1) compared to Ir or Pt, Cu as a 1st row transition metal induces much weaker spin-orbit coupling.15 As a consequence, transitions between the excited triplet state and the singlet ground state are largely forbidden. Thus, long phosphorescence decay times of several 100 μs are found. 5,6 Therefore, in an OLED, strong saturation effects would result. (2) Cu(I) complexes with reducible ligands, i.e. with energetically low-lying π* orbitals, such as aromatic diimines, often display distinct low-energy metal-toligand charge-transfer (MLCT) transitions in the visible part of the spectrum. With this type of electronic excitation, a flattening distortion of the molecular structure takes place.13a, [16][17][18] Such structural rearrangements are usually connected with an increase of non-radiative deactivation or even quenching of the emission due to an increase of the Franck-Condon factors that couple the excited state and the ground state. 19,20 This is especially distinct in non-rigid environments. 21This contribution presents a new, adequately designe...

Boron clusters are polyhedral boron hydrides with unique properties, and they are becoming increasingly widely used in biology and medicine, including for boron neutron capture therapy (BNCT) of cancers and in the design of novel bioactive molecules and potential drugs. Among boron cluster types, icosahedral boranes, carboranes, and metallacarboranes are particularly interesting, and there is a need for basic studies on their interaction with biologically important molecules, such as proteins. Herein, we report studies on the interaction of selected boron clusters and their derivatives with serum albumin, the most abundant protein in mammalian blood. The interaction of boron clusters with albumin was examined by fluorescence quenching, circular dichroism, dynamic and static light scattering measurements and MALDI-TOF mass spectrometry. Our results showed that metallacarboranes have the strongest interaction with albumin among the tested clusters. The observed strength of boron cluster interactions with albumin decreases in order: metallacarboranes [M(C2B9H11)2]− > carboranes (C2B10H12) >> dodecaborate anion [B12H12]2−. Metallacarboranes first specifically interact with the binding cavity of albumin and then, with increasing compound concentrations, interact non-specifically with the protein surface. These findings can be of importance and are useful in the development of new bioactive compounds that contain boron clusters.

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Ru(CHdCHFc)Cl(CO)(P i Pr 3) 2 (Fc = ferrocenyl, (η 5-C 5 H 4)Fe(η 5-C 5 H 5)), 1, has been prepared by hydroruthenation of ethynylferrocene and characterized by NMR, IR, ESI-MS, and Moessbauer spectroscopy and by X-ray crystallography. Complex 1 features conjoined ferrocene and (vinyl)ruthenium redox sites and undergoes two consecutive reversible oxidations. Pure samples of crystalline, monooxidized 1 •+ have been prepared by chemical oxidation of 1 with the ferrocenium ion. Structural comparison with 1 reveals an increase of Fe-C and Fe-Cp centr. bond lengths and ring tilting of the Cp decks, as is typical of ferrocenium ions, but also a discernible lengthening of the Ru-C(CO) and Ru-P bonds and a shortening of the Ru-C(vinyl) bond upon oxidation. This supports the general idea of charge delocalization over both redox sites in 1 •+. Band shifts of the charge-sensitive IR labels (ν(CO) for Ru, ν(C-H, Cp) for Fc), the rather small g-anisotropy in the ESR spectrum of 1 •+ , and the results of quantum chemical calculations indicate that in solution the positive charge partly resides on the vinyl ruthenium moiety. Comparison of IR shifts in the solid state and in solution and the quadrupole splitting in the Moessbauer spectrum of powdered 1 •+ point to a larger extent of charge localization on the ferrocenyl site in solid samples. This is probably due to CH 3 3 3 F hydrogen bonding interactions between the cyclopentadienyl hydrogen atoms of the radical cations and the PF 6 counterions. Monooxidized 1 •+ displays low-energy electronic absorption bands at 1370 and 2150 nm. According to quantum chemical calculations, the underlying transitions are largely localized on the ferrocene part of the molecule with only little charge transfer into the vinyl ruthenium subunit. The second oxidation is more biased toward the (vinyl)ruthenium site.