PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “PHOSPHORESCENCE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources
PubMed1982

Spectroscopy of (carbon monoxy)hemocyanins. Phosphorescence of the binuclear carbonylated copper centers.

The luminescence of CO-hemocyanin has been studied in several hemocyanins from both arthropods and molluscs. All of them show an emission in the region 550-560 nm with quantum yield = 0.2-0.4, though individual differences are apparent. Solvent composition (as well as the presence of calcium and lanthanides) has no effect on the emission. Lifetimes of this luminescence are in the range 60-140 microseconds, indicating that the emitting state may be a triplet. The presence of both copper atoms (Cu+) per CO binding site is required for the luminescent state since half-met and half-apo derivatives do not show such an emission. Though not clearly related to any of the functional properties, systematic differences in luminescence parameters are apparent between arthropodal and molluscan hemocyanins. Limulus hemocyanin appears to be very different from both types of hemocyanin.

Animals↗
PubMed2002

Synthesis and characterization of phosphorescent cyclometalated platinum complexes.

The synthesis, electrochemistry, and photophysics of a series of square planar Pt(II) complexes are reported. The complexes have the general structure C(wedge)NPt(O(wedge)O),where C(wedge)N is a monoanionic cyclometalating ligand (e.g., 2-phenylpyridyl, 2-(2'-thienyl)pyridyl, 2-(4,6-difluorophenyl)pyridyl, etc.) and O(wedge)O is a beta-diketonato ligand. Reaction of K(2)PtCl(4) with a HC(wedge)N ligand precursor forms the chloride-bridged dimer, C(wedge)NPt(mu-Cl)(2)PtC(wedge)N, which is cleaved with beta-diketones such as acetyl acetone (acacH) and dipivaloylmethane (dpmH) to give the corresponding monomeric C(wedge)NPt(O(wedge)O) complex. The thpyPt(dpm) (thpy = 2-(2'-thienyl)pyridyl) complex has been characterized using X-ray crystallography. The bond lengths and angles for this complex are similar to those of related cyclometalated Pt complexes. There are two independent molecular dimers in the asymmetric unit, with intermolecular spacings of 3.45 and 3.56 A, consistent with moderate pi-pi interactions and no evident Pt-Pt interactions. Most of the C(wedge)NPt(O(wedge)O) complexes display a single reversible reduction wave between -1.9 and -2.6 V (vs Cp(2)Fe/Cp(2)Fe(+)), assigned to largely C(wedge)N ligand based reduction, and an irreversible oxidation, assigned to predominantly Pt based oxidation. DFT calculations were carried out on both the ground (singlet) and excited (triplet) states of these complexes. The HOMO levels are a mixture of Pt and ligand orbitals, while the LUMO is predominantly C(wedge)N ligand based. The emission characteristics of these complexes are governed by the nature of the organometallic cyclometalating ligand allowing the emission to be tuned throughout the visible spectrum. Twenty-three different C(wedge)N ligands have been examined, which gave emission lambda(max) values ranging from 456 to 600 nm. Well-resolved vibronic fine structure is observed in all of the emission spectra (room temperature and 77 K). Strong spin-orbit coupling of the platinum atom allows for the formally forbidden mixing of the (1)MLCT with the (3)MCLT and (3)pi-pi states. This mixing leads to high emission quantum efficiencies (0.02-0.25) and lifetimes on the order of microseconds for the platinum complexes.

Journal Article↗