TY - JOUR
T1 - Quinoxalino[2,3-b′]porphyrins behave as π-expanded porphyrins upon one-electron reduction
T2 - Broad control of the degree of derealization through substitution at the macrocycle periphery
AU - Kadish, Karl M.
AU - Wenbo, E.
AU - Static, Paul J.
AU - Ou, Zhongping
AU - Shao, Jianguo
AU - Ohkubo, Kei
AU - Fukuzumi, Shunichi
AU - Govenlock, Linda J.
AU - McDonald, James A.
AU - Try, Andrew C.
AU - Cai, Zheng Li
AU - Reimers, Jeffrey R.
AU - Crossley, Maxwell J.
PY - 2007/8/2
Y1 - 2007/8/2
N2 - The synthesis and redox properties of a series of free-base and metal(II) quinoxalino[2,3-b′]porphyrins and their use in an investigation of the substituent effects on the degree of communication between the porphyrin and its β,β′-fused quinoxalino component are reported. ESR, thin-layer spectroelectrochemistry, and quantum chemical calculations of the resultant radical anions from one-electron reduction indicate that localization of the unpaired electron across both the porphyrin and the fused quinoxalino group can be controlled, the system as a whole behaving as a highly polarizable π-expanded porphyrin radical anion. ESR studies on the radical anions of zinc(II) quinoxalino[2,3-b′]porphyrin derivatives indicate that nitrogen-atom spin distribution changes as a function of chemical substitution: 27% quinoxaline character when the porphyrin ring bears a 7-nitro substituent, 34% quinoxaline character in the unsubstituted parent, and 51-61% nitroquinoxaline character when the quinoxalino unit has one or more nitro groups. Close analogies are found between the calculated and observed nitrogen-atom spin distributions, indicating that the calculations embody the key chemical effects. The calculations also indicate that the nitrogen-atom spin distributions closely parallel the important total porphyrin, quinoxaline, and nitro spin distributions, indicating that the observed quantities realistically depict the change in the nature of the delocalization of the radical anion as a function of chemical substitution. The profound effects observed indicate long-range communication of the type that is essential in molecular electronics applications.
AB - The synthesis and redox properties of a series of free-base and metal(II) quinoxalino[2,3-b′]porphyrins and their use in an investigation of the substituent effects on the degree of communication between the porphyrin and its β,β′-fused quinoxalino component are reported. ESR, thin-layer spectroelectrochemistry, and quantum chemical calculations of the resultant radical anions from one-electron reduction indicate that localization of the unpaired electron across both the porphyrin and the fused quinoxalino group can be controlled, the system as a whole behaving as a highly polarizable π-expanded porphyrin radical anion. ESR studies on the radical anions of zinc(II) quinoxalino[2,3-b′]porphyrin derivatives indicate that nitrogen-atom spin distribution changes as a function of chemical substitution: 27% quinoxaline character when the porphyrin ring bears a 7-nitro substituent, 34% quinoxaline character in the unsubstituted parent, and 51-61% nitroquinoxaline character when the quinoxalino unit has one or more nitro groups. Close analogies are found between the calculated and observed nitrogen-atom spin distributions, indicating that the calculations embody the key chemical effects. The calculations also indicate that the nitrogen-atom spin distributions closely parallel the important total porphyrin, quinoxaline, and nitro spin distributions, indicating that the observed quantities realistically depict the change in the nature of the delocalization of the radical anion as a function of chemical substitution. The profound effects observed indicate long-range communication of the type that is essential in molecular electronics applications.
UR - http://www.scopus.com/inward/record.url?scp=34548253929&partnerID=8YFLogxK
U2 - 10.1021/jp0726743
DO - 10.1021/jp0726743
M3 - Article
C2 - 17608523
AN - SCOPUS:34548253929
SN - 1520-6106
VL - 111
SP - 8762
EP - 8774
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 30
ER -