MLCT excited states of cuprous bis-phenanthroline coordination compounds
TL;DR: In this article, a 5-coordinate excited state complex, or exciplex, is proposed to account for temperature dependent quenching data of bis-phenanthroline (dπ)6 transition metal compounds.
About: This article is published in Coordination Chemistry Reviews.The article was published on 2000-10-01. It has received 375 citations till now. The article focuses on the topics: Excited state & Ground state.
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TL;DR: It is demonstrated that increasing the distance between donor (D) and acceptor (A) in intramolecular-charge-transfer molecules is a promising strategy for simultaneously achieving small ΔE(ST) and large k(F), which is in good agreement with those predicted by corrected time-dependent density functional theory.
Abstract: Red fluorescent molecules suffer from large, non-radiative internal conversion rates (kIC) governed by the energy gap law. To design efficient red thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs), a large fluorescence rate (kF) as well as a small energy difference between the lowest singlet and triplet excited states (ΔEST) is necessary. Herein, we demonstrated that increasing the distance between donor (D) and acceptor (A) in intramolecular-charge-transfer molecules is a promising strategy for simultaneously achieving small ΔEST and large kF. Four D-Ph-A-Ph-D-type molecules with an anthraquinone acceptor, phenyl (Ph) bridge, and various donors were designed, synthesized, and compared with corresponding D-A-D-type molecules. Yellow to red TADF was observed from all of them. The kF and ΔEST values determined from the measurements of quantum yield and lifetime of the fluorescence and TADF components are in good agreement with those predicted by corrected tim...
750 citations
TL;DR: New, readily accessible copper(I) complexes that can exhibit unusually long-lived, high quantum yield emissions in fluid solution are described.
Abstract: This report describes new, readily accessible copper(I) complexes that can exhibit unusually long-lived, high quantum yield emissions in fluid solution. The complexes are of the form [Cu(NN)(POP)]+ where NN denotes 1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (dmp) or 2,9-di-n-butyl-1,10-phenanthroline (dbp) and POP denotes bis[2-(diphenylphosphino)phenyl] ether. Modes of characterization include X-ray crystallography and cyclic voltammetry. The complexes each have a pseudotetrahedral coordination geometry and a Cu(II)/Cu(I) potential upward of +1.2 V vs Ag/AgCl. In room-temperature dichloromethane solution, charge-transfer excited states of the dmp and dbp derivatives exhibit respective emission quantum yields of 0.15 and 0.16 and corresponding excited-state lifetimes of 14.3 and 16.1 μs, respectively. Despite the fact that coordinating solvents usually quench charge-transfer emission from copper systems, the photoexcited dmp (dbp) complex retains a lifetime of 2.4 μs (5.4 μs) in methanol.
576 citations
TL;DR: This work focuses on some selected examples of Cu(I, Ag(I), Au(I%), Zn(II) and Cd( II) luminescent complexes to suggest some possible routes towards promising and unprecedented emitting materials.
538 citations
01 Jan 2007
TL;DR: In this paper, the authors compare the properties of copper compounds and clusters and point out the limited significance of Cu(II) compounds in terms of photophysical properties, pointing out the criteria by which it is now possible to successfully design highly emissive [Cu(NN)2]- compounds, a rather elusive goal for a long time.
Abstract: Cu(I) complexes and clusters are the largest class of compounds of relevant photochemical and photophysical interest based on a relatively abundant metal element. Interestingly, Nature has given an essential role to copper compounds in some biological systems, relying on their kinetic lability and versatile coordination environment. Some basic properties of Cu(I) and Cu(II) such as their coordination geometries and electronic levels are compared, pointing out the limited significance of Cu(II) compounds (d 9 configuration) in terms of photophysical properties. Well-established synthetic protocols are available to build up a variety of molecular and supramolecular architectures (e.g. catenanes, rotaxanes, knots, helices, dendrimers, cages, grids, racks, etc.) containing Cu(I)-based centers and exhibiting photo- and electroluminescence as well as light-induced intercomponent processes. By far the largest class of copper complexes investigated to date is that of Cu(I)-bisphenanthrolines ([Cu(NN)2]+) and recent progress in the rationalization of their metal-to-ligand charge-transfer (MLCT) absorption and luminescence properties are critically reviewed, pointing out the criteria by which it is now possible to successfully design highly emissive [Cu(NN)2]+ compounds, a rather elusive goal for a long time. To this end the development of spectroscopic techniques such as light-initiated time-resolved X-ray absorption spectroscopy (LITR-XAS) and femtosecond transient absorption have been rather fruitful since they have allowed us to firmly ground the indirect proofs of the molecular rearrangements following light absorption that had accumulated in the past 20 years. A substantial breakthrough towards highly emissive Cu(I) coordination compounds is constituted by heteroleptic Cu(I) complexes containing both N- and P-coordinating ligands ([Cu(NN)(PP)]+) which may exhibit luminescence quantum yields close to 30% in deaerated CH2Cl2 solution and have been successfully employed as active materials in OLED and LEC optoelectronic devices. Also copper clusters may exhibit luminescence bands of halide-to-metal charge transfer (XMCT) and/or cluster centered (CC) character and they are briefly reviewed along with miscellaneous Cu(I) compounds that recently appeared in the literature, which show luminescence bands ranging from the blue to the red spectral region.
491 citations
TL;DR: Through the systematic study on the variation of ligands, structural and bonding modes of different metal centres, the structure-property relationships of the various classes of luminescent transition metal complexes can be obtained and their electronic absorption and luminescence properties can be fine-tuned.
451 citations
References
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Book•
01 Jan 1983
TL;DR: This book describes the fundamental aspects of fluorescence, the biochemical applications of this methodology, and the instrumentation used in fluorescence spectroscopy.
Abstract: Fluorescence methods are being used increasingly in biochemical, medical, and chemical research. This is because of the inherent sensitivity of this technique. and the favorable time scale of the phenomenon of fluorescence. 8 Fluorescence emission occurs about 10- sec (10 nsec) after light absorp tion. During this period of time a wide range of molecular processes can occur, and these can effect the spectral characteristics of the fluorescent compound. This combination of sensitivity and a favorable time scale allows fluorescence methods to be generally useful for studies of proteins and membranes and their interactions with other macromolecules. This book describes the fundamental aspects of fluorescence. and the biochemical applications of this methodology. Each chapter starts with the -theoreticalbasis of each phenomenon of fluorescence, followed by examples which illustrate the use of the phenomenon in the study of biochemical problems. The book contains numerous figures. It is felt that such graphical presentations contribute to pleasurable reading and increased understand ing. Separate chapters are devoted to fluorescence polarization, lifetimes, quenching, energy transfer, solvent effects, and excited state reactions. To enhance the usefulness of this work as a textbook, problems are included which illustrate the concepts described in each chapter. Furthermore, a separate chapter is devoted to the instrumentation used in fluorescence spectroscopy. This chapter will be especially valuable for those perform ing or contemplating fluorescence measurements. Such measurements are easily compromised by failure to consider a number of simple principles."
28,073 citations
TL;DR: In this article, the authors describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency.
Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.
26,457 citations
Book•
01 Jan 1980
TL;DR: In this paper, the authors present a comprehensive overview of electrode processes and their application in the field of chemical simulation, including potential sweep and potential sweep methods, coupled homogeneous chemical reactions, double-layer structure and adsorption.
Abstract: Major Symbols. Standard Abbreviations. Introduction and Overview of Electrode Processes. Potentials and Thermodynamics of Cells. Kinetics of Electrode Reactions. Mass Transfer by Migration and Diffusion. Basic Potential Step Methods. Potential Sweep Methods. Polarography and Pulse Voltammetry. Controlled--Current Techniques. Method Involving Forced Convention--Hydrodynamic Methods. Techniques Based on Concepts of Impedance. Bulk Electrolysis Methods. Electrode Reactions with Coupled Homogeneous Chemical Reactions. Double--Layer Structure and Adsorption. Electroactive Layers and Modified Electrodes. Electrochemical Instrumentation. Scanning Probe Techniques. Spectroelectrochemistry and Other Coupled Characterization Methods. Photoelectrochemistry and Electrogenerated Chemiluminescence. Appendix A: Mathematical Methods. Appendix B: Digital Simulations of Electrochemical Problems. Appendix C: Reference Tables. Index.
20,533 citations
Book•
01 Jan 1999
TL;DR: Cotton and Wilkinson's Advanced Inorganic Chemistry (AIC) as discussed by the authors is one of the most widely used inorganic chemistry books and has been used for more than a quarter century.
Abstract: For more than a quarter century, Cotton and Wilkinson's Advanced Inorganic Chemistry has been the source that students and professional chemists have turned to for the background needed to understand current research literature in inorganic chemistry and aspects of organometallic chemistry. Like its predecessors, this updated Sixth Edition is organized around the periodic table of elements and provides a systematic treatment of the chemistry of all chemical elements and their compounds. It incorporates important recent developments with an emphasis on advances in the interpretation of structure, bonding, and reactivity.From the reviews of the Fifth Edition:* "The first place to go when seeking general information about the chemistry of a particular element, especially when up-to-date, authoritative information is desired." -Journal of the American Chemical Society.* "Every student with a serious interest in inorganic chemistry should have [this book]." -Journal of Chemical Education.* "A mine of information . . . an invaluable guide." -Nature.* "The standard by which all other inorganic chemistry books are judged."-Nouveau Journal de Chimie.* "A masterly overview of the chemistry of the elements."-The Times of London Higher Education Supplement.* "A bonanza of information on important results and developments which could otherwise easily be overlooked in the general deluge of publications." -Angewandte Chemie.
12,231 citations
4,395 citations