160 research outputs found
Absorption Spectra, Photophysical Properties, and Redox Behavior of Ruthenium(II) Polypyridine Complexes Containing Accessory Dipyrromethene-BF2 Chromophores
No full textThe six multichromophoric species 1-6, containing the potentially luminescent Ru(II) polypyridine subunits and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene fluorophores (dipyrromethene-BF2 dyes, herein after called bodipy), have been prepared and their absorption spectra, luminescence properties (both at room temperature in fluid solution and at 77 K in rigid matrix), and redox properties have been investigated (for the structural formulas of all the compounds, see Figure 1). For comparison purposes, also the same properties of the bodipy-based free ligands have been examined. Three of the multichromophoric species (1-3) are based on the Ru(bpy)3-type metal subunit, whereas 4-6 are based on the Ru(terpy)2-type metal subunit. Transient absorption spectroscopy at room temperature of all the compounds has also been performed. The absorption spectra of all the metal complexes show features that can be assigned to the Ru(II) polypyridine subunits and to the bodipy centers. In particular, the lowest energy spin-allowed -* transition of the bodipy groups dominates the visible region, peaking at about 530 nm. All the new complexes exhibit a rich redox behavior, with reversible processes attributed to specific sites, indicating a small perturbation of each redox center and therefore highlighting the supramolecular nature of the multichromophoric assemblies. Despite the good luminescence properties of the separated components, 1-6 do not exhibit any luminescence at room temperature; however, transient absorption spectroscopy evidences that for all of them a long-lived (microsecond time scale) excited state is formed, which is identified as the bodipy-based triplet state. Pump-probe transient absorption spectroscopy suggests that such a triplet state is formed from the promptly prepared bodipy-based 1-* state in most cases by the intervention of a charge-separated level. At 77 K, all the complexes except complex 1 exhibit the bodipy-based fluorescence, although with a slightly shortened lifetime compared to the corresponding free ligand(s), and 4-6 also exhibit a phosphorescence assigned to the bodipy subunits. Phosphorescence of bodipy species had never been reported in the literature to the best of our knowledge: in the present cases we propose that it is an effective decay process thanks to the presence of the ruthenium heavy atom and of the closely lying 3MLCT state of the Ru(terpy)2-type subunits
Replication data/material for Maredia et al. (2022)'s JAAEA, "Preferences for Pandemic Recovery Policies: Perspectives of Myanmar Agri-food System Participants."
No full textThis data repository contains replication data and material for Maredia, Goeb, Ortega, Synt, and Zu (2022)'s JAAEA paper, titled "Preferences for Pandemic Recovery Policies: Perspectives of Myanmar Agri-food System Participants.
Biblia, Das ist: Die ganze Göttliche Heilige Schrifft, Alten und Neuen Testaments, nach der deutschen Uebersetzung Dr. Martin Luthers Mit jedes Capitels kurzen Summarien, auch beygefügten vielen und richtigen Paralellen. Nebst schicklichen Nutzanwendungen zu den fünf Büchern Mosis, dem Hohelied Salomonis und der Offenbarung S. Johannis
No full textControlling the Guest Release from Electro-Active Self-Assembled Cages
Get PDFControlling the Guest Release from Electro-Active Self-Assembled Cages</p
Electronic Energy Transfer to the S<sub>2</sub> Level of the Acceptor in Functionalised Boron Dipyrromethene Dyes
No full textA multi-component array has been constructed around an expanded boron dipyrromethene (Bodipy) dye that absorbs and emits in the far-red region. One of the appendages is a perylene-based moiety that is connected to the boron atom of the terminal Bodipy by a 1,4-diethynylphenylene connector. Despite the fact that there is almost negligible spectral overlap between fluorescence from the perylene unit and absorption by the Bodipy residue, electronic energy transfer is rapid and essentially quantitative. It is concluded that at least half of the photons absorbed by perylene are transferred to the upper-lying singlet excited state (S-2) associated with the Bodipy-based acceptor. The second appendage is a pyrene unit that is covalently linked to fluorene, through an ethynylene spacer, and to the boron atom of the Bodipy terminus, through a 1,4-diethynylphenylene connector. Pyrene absorbs and emits at higher energy than perylene and there is strong spectral overlap with the Bodipy-based S-2 state, and none with the corresponding S-1 state. Electronic energy transfer is now very fast and exclusively to the S-2 state of the acceptor. It is difficult to compute reasonable estimates for the rates of Coulombic energy transfer, because of uncertainties in the orientation factor, but the principle mechanism is believed to arise from electron exchange. Comparison with an earlier array built around a conventional Bodipy dye indicates that there are comparable electronic coupling matrix elements for the two systems. It is notable that pyrene is more strongly coupled to the Bodipy unit than perylene in both arrays. These new arrays function as highly effective solar concentrators
Encapsulation/relargage réversible d’un invité par contrôle redox de l’assemblage/ désas-semblage d’une cage de coordination
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Colouration and decolouration processes in gas pressure sintered silicon nitride ceramics
No full textS.47-486
Diversity and distribution of Asian Lejeuneaceae subfamily Ptychanthoideae
No full textA synopsis is provided of 88 species in 17 genera currently recognized in Lejeuneaceae subfamily Ptychanthoideae sensu lato (including Nipponolejeunea) of Asia. Taxonomic novelties include Thysananthus flavescens (Hatt.) comb. nov. (for Mastigolejeunea flavescens (Hatt.) Mizut.), Spruceanthus macrostipulus (Steph.) comb. nov. (for Archilejeunea macrostipula (Steph.) Verd.) and the reduction of Platylejeunea Mizut. to synonymy under Lopholejeunea
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