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Special Issue "Fluorescent Metal-Ligand Complexes"

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (30 June 2010)

Special Issue Editor

Guest Editor
Dr. Grzegorz Piszczek

Biophysics Facility Head, Biochemistry and Biophysics Center, NHLBI/NIH, 50 South Dr, Rm. 2341, MSC-8012 Bethesda, MD 20892-8012, USA
Phone: +1 301 435 8082
Fax: +1 301 496 0599

Special Issue Information

Dear Colleagues,

Fluorescence spectroscopy is the most popular optical spectroscopy method in research and analytical measurements. The wide range of research applications includes studies of structure, conformation dynamics and stability of biomolecules. Fluorescence is applied to study interactions and structure-function relationships of proteins and nucleic acids. In analytical applications it is used in trace element detection and DNA sequencing. In clinical laboratories fluorescence immunoassays are successfully replacing radioimmunoassay techniques. New applications of fluorescence usually require fluorescent probes with specific properties and while there are numerous organic fluorophores available, most of them display fluorescence lifetimes in the 1 ns to 10 ns range. Discovery of a long-lifetime polarized emission of Metal-Ligand Complexes opened a new window into the dynamic information content of fluorescence. It also allowed the MLCs fluorescence to be applied in gated detection and immunoassays. An important advantage of MLCs fluorophores is their high chemical and photochemical stability under physiological conditions. Various MLC based probes were successfully applied to measure protein-protein interactions and to obtain molecular dynamics information about proteins, DNA and lipid bilayers systems. Fluorescent MLCs remain the only class of fluorescent probes with a number of favorable properties; they have fluorescence lifetimes in the 10 ns to 1000 ns range, polarized emission, large Stocks shifts, and their absorption coefficients are high enough to allow an efficient direct excitation.

The source of MLCs fluorescence is the metal-to-ligand charge-transfer state and a careful selection of metal and ligands can generate MLCs with favorable spectroscopic and physical properties. Many laboratories continue to work on the development of new MLC based probes. Newly synthesized probes often have higher quantum efficiency, increased emission anisotropy and their properties are tailored to specific applications in biological and medical research. In this issue we explore the current progress in synthesis, characterization and applications of fluorescent Metal-Ligand Complexes.

Dr. Grzegorz Piszczek
Guest Editor

Keywords

  • metal-ligand complex
  • metal-ligand probes
  • long lifetime probes
  • fluorescence
  • polarization
  • anisotropy

Published Papers (2 papers)

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Research

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Open AccessArticle Fluorescence and FTIR Spectra Analysis of Trans-A2B2-Substituted Di- and Tetra-Phenyl Porphyrins
Materials 2010, 3(8), 4446-4475; doi:10.3390/ma3084446
Received: 29 June 2010 / Revised: 9 August 2010 / Accepted: 20 August 2010 / Published: 23 August 2010
Cited by 8 | PDF Full-text (660 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A series of asymmetrically substituted free-base di- and tetra-phenylporphyrins and the associated Zn-phenylporphyrins were synthesized and studied by X-ray diffraction, NMR, infrared, electronic absorption spectra, as well as fluorescence emission spectroscopy, along with theoretical simulations of the electronic and vibration structures. The [...] Read more.
A series of asymmetrically substituted free-base di- and tetra-phenylporphyrins and the associated Zn-phenylporphyrins were synthesized and studied by X-ray diffraction, NMR, infrared, electronic absorption spectra, as well as fluorescence emission spectroscopy, along with theoretical simulations of the electronic and vibration structures. The synthesis selectively afforded trans-A2B2 porphyrins, without scrambling observed, where the AA and BB were taken as donor- and acceptor-substituted phenyl groups. The combined results point to similar properties to symmetrically substituted porphyrins reported in the literature. The differences in FTIR and fluorescence were analyzed by means of detailed density functional theory (DFT) calculations. The X-ray diffraction analysis for single crystals of zinc-containing porphyrins revealed small deviations from planarity for the porphyrin core in perfect agreement with the DFT optimized structures. All calculated vibrational modes (2162 modes for all six compounds studied) were found and fully characterized and assigned to the observed FTIR spectra. The most intense IR bands are discussed in connection with the generic similarity and differences of calculated normal modes. Absorption spectra of all compounds in the UV and visible regions show the typical ethio type feature of meso-tetraarylporphyrins with a very intense Soret band and weak Q bands of decreasing intensity. In diphenyl derivatives, the presence of only two phenyl rings causes a pronounced hypsochromic shift of all bands in the absorption spectra. Time-dependent DFT calculations revealed some peculiarities in the electronic excited states structure and connected them with vibronic bands in the absorption and fluorescence spectra from associated vibrational sublevels. Full article
(This article belongs to the Special Issue Fluorescent Metal-Ligand Complexes)

Review

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Open AccessReview Emission Spectroscopy as a Probe into Photoinduced Intramolecular Electron Transfer in Polyazine Bridged Ru(II),Rh(III) Supramolecular Complexes
Materials 2010, 3(8), 4328-4354; doi:10.3390/ma3084328
Received: 5 July 2010 / Accepted: 2 August 2010 / Published: 11 August 2010
Cited by 7 | PDF Full-text (546 KB) | HTML Full-text | XML Full-text
Abstract
Steady-state and time-resolved emission spectroscopy are valuable tools to probe photochemical processes of metal-ligand, coordination complexes. Ru(II) polyazine light absorbers are efficient light harvesters absorbing in the UV and visible with emissive 3MLCT excited states known to undergo excited state energy [...] Read more.
Steady-state and time-resolved emission spectroscopy are valuable tools to probe photochemical processes of metal-ligand, coordination complexes. Ru(II) polyazine light absorbers are efficient light harvesters absorbing in the UV and visible with emissive 3MLCT excited states known to undergo excited state energy and electron transfer. Changes in emission intensity, energy or band-shape, as well as excited state lifetime, provide insight into excited state dynamics. Photophysical processes such as intramolecular electron transfer between electron donor and electron acceptor sub-units may be investigated using these methods. This review investigates the use of steady-state and time-resolved emission spectroscopy to measure excited state intramolecular electron transfer in polyazine bridged Ru(II),Rh(III) supramolecular complexes. Intramolecular electron transfer in these systems provides for conversion of the emissive 3MLCT (metal-to-ligand charge transfer) excited state to a non-emissive, but potentially photoreactive, 3MMCT (metal-to-metal charge transfer) excited state. The details of the photophysics of Ru(II),Rh(III) and Ru(II),Rh(III),Ru(II) systems as probed by steady-state and time-resolved emission spectroscopy will be highlighted. Full article
(This article belongs to the Special Issue Fluorescent Metal-Ligand Complexes)

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