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Statements

Subject Item
n2:RIV%2F60076658%3A12310%2F12%3A43884437%21RIV13-MSM-12310___
rdf:type
n13:Vysledek skos:Concept
dcterms:description
The photophysics of the two isomers of octadecaborane(22), anti- and syn-B18H22, have been studied by UV-vis spectroscopic techniques and theoretical computational methods. In air-saturated hexane, anti-B18H22 shows fluorescence with a high quantum yield, Phi(F) = 0.97, and singlet oxygen O-2((1)Delta(g)) production (Phi(Delta) similar to 0.008). Conversely, isomer syn-B18H22 shows no measurable fluorescence, instead displaying much faster, picosecond non-adiative decay of excited singlet states. Computed potential energy hypersurfaces (PEHs) for both isomers rationalize these data, pointing to a deep S-1 minimum for anti-B18H22 and a conical intersection (CI) between its S-0 and S-1 states that lies 0.51 eV higher in energy. Such an energy barrier to nonradiative relaxation is not present in the PEH of syn-B18H22, and the system therefore has sufficient initial energy on excitation to reach the (S-0/S-1) CI and to then decay to the ground state without fluorescence. The computational analysis of the geometries at stationary points along the PEH of both isomers shows that the determining factor for the dissimilar photophysics of anti- and syn-B18H22 may be due to the significant differences in the geometrical rearrangements at their respective conical intersections. Thus, the syn isomer shows one very large, B B elongation of 1.2 angstrom from 1.8 angstrom in the ground state to 3.0 angstrom at the CI, whereas the anti isomer shows smaller elongations (below 1 angstrom) in several B-B connectivities at its (S-0/S-1)(CI). The absorbed energy in SI for the anti-B18H22 is therefore redistributed vibrationally into several regions of the molecule rather than almost completely into a single vibrational mode as in the case for the syn isomer. The consequent prolonged S-1 lifetime for the anti isomer allows for relaxation via fluorescence. The photophysics of the two isomers of octadecaborane(22), anti- and syn-B18H22, have been studied by UV-vis spectroscopic techniques and theoretical computational methods. In air-saturated hexane, anti-B18H22 shows fluorescence with a high quantum yield, Phi(F) = 0.97, and singlet oxygen O-2((1)Delta(g)) production (Phi(Delta) similar to 0.008). Conversely, isomer syn-B18H22 shows no measurable fluorescence, instead displaying much faster, picosecond non-adiative decay of excited singlet states. Computed potential energy hypersurfaces (PEHs) for both isomers rationalize these data, pointing to a deep S-1 minimum for anti-B18H22 and a conical intersection (CI) between its S-0 and S-1 states that lies 0.51 eV higher in energy. Such an energy barrier to nonradiative relaxation is not present in the PEH of syn-B18H22, and the system therefore has sufficient initial energy on excitation to reach the (S-0/S-1) CI and to then decay to the ground state without fluorescence. The computational analysis of the geometries at stationary points along the PEH of both isomers shows that the determining factor for the dissimilar photophysics of anti- and syn-B18H22 may be due to the significant differences in the geometrical rearrangements at their respective conical intersections. Thus, the syn isomer shows one very large, B B elongation of 1.2 angstrom from 1.8 angstrom in the ground state to 3.0 angstrom at the CI, whereas the anti isomer shows smaller elongations (below 1 angstrom) in several B-B connectivities at its (S-0/S-1)(CI). The absorbed energy in SI for the anti-B18H22 is therefore redistributed vibrationally into several regions of the molecule rather than almost completely into a single vibrational mode as in the case for the syn isomer. The consequent prolonged S-1 lifetime for the anti isomer allows for relaxation via fluorescence.
dcterms:title
Distinct Photophysics of the Isomers of B18H22 Explained Distinct Photophysics of the Isomers of B18H22 Explained
skos:prefLabel
Distinct Photophysics of the Isomers of B18H22 Explained Distinct Photophysics of the Isomers of B18H22 Explained
skos:notation
RIV/60076658:12310/12:43884437!RIV13-MSM-12310___
n13:predkladatel
n14:orjk%3A12310
n4:aktivita
n10:Z n10:P
n4:aktivity
P(GAP207/11/1577), P(GAP208/10/1678), Z(AV0Z40320502), Z(AV0Z40400503), Z(MSM6007665808)
n4:cisloPeriodika
3
n4:dodaniDat
n8:2013
n4:domaciTvurceVysledku
n7:4395263
n4:druhVysledku
n21:J
n4:duvernostUdaju
n6:S
n4:entitaPredkladatele
n18:predkladatel
n4:idSjednocenehoVysledku
131571
n4:idVysledku
RIV/60076658:12310/12:43884437
n4:jazykVysledku
n19:eng
n4:klicovaSlova
oxygen; absorption; state; quantum yields; molecular-structure; photodynamic therapy; 2nd-order perturbation-theory
n4:klicoveSlovo
n5:state n5:oxygen n5:quantum%20yields n5:2nd-order%20perturbation-theory n5:absorption n5:molecular-structure n5:photodynamic%20therapy
n4:kodStatuVydavatele
US - Spojené státy americké
n4:kontrolniKodProRIV
[3CB06A2E3480]
n4:nazevZdroje
Inorganic Chemistry
n4:obor
n16:BO
n4:pocetDomacichTvurcuVysledku
1
n4:pocetTvurcuVysledku
9
n4:projekt
n15:GAP208%2F10%2F1678 n15:GAP207%2F11%2F1577
n4:rokUplatneniVysledku
n8:2012
n4:svazekPeriodika
51
n4:tvurceVysledku
Bould, Jonathan Hnyk, Drahomir Oliva, Josep M. Serrano-Andres, Luis Kubat, Pavel Londesborough, Michael G. S. Polívka, Tomáš Sauri, Vicenta Lang, Kamil
n4:wos
000300474700038
n4:zamer
n11:AV0Z40320502 n11:AV0Z40400503 n11:MSM6007665808
s:issn
0020-1669
s:numberOfPages
9
n12:doi
10.1021/ic201726k
n3:organizacniJednotka
12310