skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Luminescence from the trans-Dioxotechnetium(V) Chromophore

Abstract

Photophysical properties of the trans-dioxotechnetium(V) chromophore are reported for the first time. The complexes [TcO₂(L)₄] ⁺ (L=pyridine or 4-picoline) and [TcO₂(CN)₄]³ ⁻ are luminescent from a ³Eg excited state in the near IR with emission maxima ranging from 715-750 nm. DFT calculations predicted the observed red-shift in emission energy relative to trans-dioxorhenium(V) congeners. Distinct vibronic progressions are observed in the symmetric O=Tc=O and Tc-L stretching frequencies in the 8 K emission spectra and excited state lifetimes mirrored trends of the analogous Re(V) complexes.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
876941
Report Number(s):
PNNL-SA-45787
Journal ID: ISSN 0002-7863; JACSAT; 12298; 13791; KP1301020; TRN: US0601432
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society, 127(43):14978-14979; Journal Volume: 127; Journal Issue: 43
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; EMISSION SPECTRA; EXCITED STATES; LUMINESCENCE; TECHNETIUM COMPLEXES; DENSITY FUNCTIONAL METHOD; Environmental Molecular Sciences Laboratory

Citation Formats

Del Negro, Andy S., Wang, Zheming, Seliskar, Carl J., Heineman, William R., Sullivan, Brian P., Hightower, Sean E., Hubler, Timothy L., and Bryan, Samuel A. Luminescence from the trans-Dioxotechnetium(V) Chromophore. United States: N. p., 2005. Web. doi:10.1021/ja054906m.
Del Negro, Andy S., Wang, Zheming, Seliskar, Carl J., Heineman, William R., Sullivan, Brian P., Hightower, Sean E., Hubler, Timothy L., & Bryan, Samuel A. Luminescence from the trans-Dioxotechnetium(V) Chromophore. United States. doi:10.1021/ja054906m.
Del Negro, Andy S., Wang, Zheming, Seliskar, Carl J., Heineman, William R., Sullivan, Brian P., Hightower, Sean E., Hubler, Timothy L., and Bryan, Samuel A. Wed . "Luminescence from the trans-Dioxotechnetium(V) Chromophore". United States. doi:10.1021/ja054906m.
@article{osti_876941,
title = {Luminescence from the trans-Dioxotechnetium(V) Chromophore},
author = {Del Negro, Andy S. and Wang, Zheming and Seliskar, Carl J. and Heineman, William R. and Sullivan, Brian P. and Hightower, Sean E. and Hubler, Timothy L. and Bryan, Samuel A.},
abstractNote = {Photophysical properties of the trans-dioxotechnetium(V) chromophore are reported for the first time. The complexes [TcO₂(L)₄] ⁺ (L=pyridine or 4-picoline) and [TcO₂(CN)₄]³ ⁻ are luminescent from a ³Eg excited state in the near IR with emission maxima ranging from 715-750 nm. DFT calculations predicted the observed red-shift in emission energy relative to trans-dioxorhenium(V) congeners. Distinct vibronic progressions are observed in the symmetric O=Tc=O and Tc-L stretching frequencies in the 8 K emission spectra and excited state lifetimes mirrored trends of the analogous Re(V) complexes.},
doi = {10.1021/ja054906m},
journal = {Journal of the American Chemical Society, 127(43):14978-14979},
number = 43,
volume = 127,
place = {United States},
year = {Wed Nov 02 00:00:00 EST 2005},
month = {Wed Nov 02 00:00:00 EST 2005}
}
  • Conformational changes of the retinal chromophore about the C14-C15 bond in bacteriorhodopsin (BR) have been proposed in models for the mechanism of light-driven proton transport. To determine the C14-C15 conformation in BR's L{sub 550} intermediate, the authors have examined the resonance Raman spectra of BR derivatives regenerated with retinal deuterated at the 14 and 15 positions. Vibrational calculations show that the C14-{sup 2}H and C15-{sup 2}H rocking modes form symmetric (A) and antisymmetric (B) combinations in (14,15-{sup 2}H)retinal chromophores. When there is a trans conformation about the single bond between C14 and C15 (14-s-trans), a small frequency separation or splittingmore » is observed between the A and B modes. In addition, the monodeuterium rock should appear at an unusually low frequency in the 14-{sup 2}H-labeled 14-s-cis molecules. These patterns are insensitive to computational details. Time-resolved resonance Raman spectra were obtained of BR's L{sub 550} intermediate regenerated with (14-{sup 2}H)-, (15-{sup 2}H)- and (14,15-{sup 2}H)retinal. These results show that L{sub 550} contains a 14-s-trans chromophore and suggest that only 14-2-trans structures are involved in the proton pumping photocycle of BR.« less
  • HcRed is a dimeric intrinsically fluorescent protein with origins in the sea anemone Heteractis crispa. This protein exhibits deep red absorption and emission properties. Using a combination of ensemble and single molecule methods and by varying environmental parameters such as temperature and pH, we found spectroscopic evidence for the presence of two ground state conformers, trans and cis chromophores that are in thermal equilibrium and that follow different excited-state pathways upon exposure to light. The photocycle of HcRed appears to be a combination of both kindling proteins and bright emitting GFP/GFP-like proteins: the trans chromophore undergoes light driven isomerization followedmore » by radiative relaxation with a fluorescence lifetime of 0.5 ns. The cis chromophore exhibits a photocycle similar to bright GFPs and GFP-like proteins such as enhanced GFP, enhanced YFP or DsRed, with radiative relaxation with a fluorescence lifetime of 1.5 ns, singlet-triplet deactivation on a microsecond time scale and solvent controlled protonation/deprotonation in tens of microseconds. Using single molecule spectroscopy, we identify trans and cis conformers at the level of individual moieties and show that it is possible that the two conformers can coexist in a single protein due to the dimeric nature of HcRed.« less
  • The far-red fluorescent protein mKate {lambda}{sup ex}, 588 nm; {lambda}{sub em}, 635 nm; chromophore-forming triad Met{sup 63}-Tyr{sup 64}-Gly{sup 65}, originating from wild-type red fluorescent progenitor eqFP578 (sea anemone Entacmaea quadricolor), is monomeric and characterized by the pronounced pH dependence of fluorescence, relatively high brightness, and high photostability. The protein has been crystallized at a pH ranging from 2 to 9 in three space groups, and four structures have been determined by x-ray crystallography at the resolution of 1.75--2.6 {angstrom}. The pH-dependent fluorescence of mKate has been shown to be due to reversible cis-trans isomerization of the chromophore phenolic ring. Inmore » the non-fluorescent state at pH 2.0, the chromophore of mKate is in the trans-isomeric form. The weakly fluorescent state of the protein at pH 4.2 is characterized by a mixture of trans and cis isomers. The chromophore in a highly fluorescent state at pH 7.0/9.0 adopts the cis form. Three key residues, Ser{sup 143}, Leu{sup 174}, and Arg{sup 197} residing in the vicinity of the chromophore, have been identified as being primarily responsible for the far-red shift in the spectra. A group of residues consisting of Val{sup 93}, Arg{sup 122}, Glu{sup 155}, Arg{sup 157}, Asp{sup 159}, His{sup 169}, Ile{sup 171}, Asn{sup 173}, Val{sup 192}, Tyr{sup 194}, and Val{sup 216}, are most likely responsible for the observed monomeric state of the protein in solution.« less
  • The structure of the retinal chromophore about the C{double bond}N and C{sub 14}-C{sub 15} bonds in bacteriorhodopsin's M{sub 412} intermediate has been determined by analyzing resonance Raman spectra of {sup 2}H and {sup 13}C isotopic derivatives. Normal mode calculations on 13-cis-retinal Schiff bases demonstrate that the C{sub 15}-D rock and N-C{sub Lys} stretch are strongly coupled for C{double bond}N-syn chromophores and weakly coupled for C{double bond}N-anti chromophores. When the Schiff base geometry is anti, the C{sub 25}-D rock appears as a localized resonance Raman active mode at {approx} 980 cm{sup {minus}1}, which is moderately sensitive to {sup 13}C substitution atmore » positions 14 and 15 ({approx} 7 cm{sup {minus}1}) and insensitive to {sup 13}C substitution at the {epsilon} position of lysine. When the Schiff base geometry is syn, in-phase and out-of-phase combinations of the C{sub 15}-D rock and N-C{sub Lys} stretch are predicted at {approx} 1060 and {approx} 910 cm{sup {minus}1}, respectively. The in-phase mode is more sensitive to {sup 13}C substitution at positions 14 and 15 and at the {epsilon} position of lysine. Calculations and comparison with experimental data on dark-adapted bacteriorhodopsin indicate that the in-phase mode at {approx} 1060 cm{sup {minus}1} carries the majority of the resonance Raman intensity. The authors conclude that M{sub 412} contains a 13-cis,14-s-trans,15-anti chromophore. This result supports the recently proposed C-T model for the mechanism of the proton pump in bacteriorhodopsin.« less
  • Understanding the molecular mechanism for the photoinduced transmembrane proton pump in the bacteriorhodopsin system is of fundamental importance. This study attempts to investigate the energetics of the initial step of the proton transport cycle, the photoisomerization of the retinal chromophore. The exact reaction pathway and the question of how many excited electronic states are involved in the internal conversion process are still unresolved. The problem is approached by constructing a reaction coordinate suggested by crystallographic studies for a simplified chromophore model system. The CASSCF and CASPT2 electronic structure methods are employed to calculate the energies of the four lowest lyingmore » singlet states as a function of the reaction coordinate. The effect of negatively charged protein residues on the reaction is simulated by inclusion of a negative point charge in the model. The results indicate that trans{yields}cis isomerization around the C{sub {beta}} = C{sub {gamma}} bond may be accompanied by twisting around the C{sub {alpha}}-C{sub {beta}} bond in order to drive the proton pump. The presence of a counterion does not seem to reduce the barrier for isomerization or the S{sub 0}-S{sub 1} energy difference but clearly stabilizes the cis--product. At first sight the results appear to support the idea of a participation of no other electronic states beyond S{sub 0} and first singly {pi}{pi}* excited state in the photoreaction. However, the relevance of this prediction is rather limited because of the small size of the model system. Other states of retinal, corresponding in particular to the partly doubly {pi}{pi}* excited S{sub 2} state of the model, are likely to have a vertical excitation energy similar to the first singly {pi}{pi}* excited state or even below.« less