TY - JOUR
T1 - Molecular orientation and structure of the transition moments of porphyrin derivatives with various symmetries
AU - Gryczynski, Zygmunt
AU - Paolesse, Roberto
AU - Smith, Kevin M.
AU - Bucci, Enrico
PY - 1994
Y1 - 1994
N2 - In order to determine the anisotropy in the absorption transition moments of hemes we measured the visible and UV linear dichroism of the high-symmetry porphyrin derivatives α,β,γ,δ-tetraphenylsulfonic porphyrin (D4h symmetry), deuterohemin III (iron deuteroporphyrin III chloride; C2v symmetry), and protohemin III (iron protoporphyrin III chloride; C2v symmetry) in stretched poly(vinyl alcohol) films in the 250-700-nm region. Their linear dichroism was analyzed by using either a "circular absorber" model or a linear absorption oscillator model. For α,β,γ,δ-tetraphenylsulfonic porphyrin with 4-fold symmetry the absorption anisotropy was found to be wavelength independent as for a circular absorber. Deutero- and protohemin III with C2v symmetry had a wavelength-dependent dichroism, indicating the linear type of the allowed transition moments. As expected from theoretical calculation the transitions most affected by peripheral substituents were the relatively weak Q, L, and N bands. Linear dichroism with very similar characteristics was reported earlier by us for native protohemin IX (iron protoporphyrin IX chloride) derivatives (Gryczynski et al. Photochem. Photobiol. 1993, 58, 492). It appears that the absorption of hemes should be considered as a simple combination of linear oscillators. The linear character of heme transition moments is what regulates the radiationless tryptophanheme interactions.
AB - In order to determine the anisotropy in the absorption transition moments of hemes we measured the visible and UV linear dichroism of the high-symmetry porphyrin derivatives α,β,γ,δ-tetraphenylsulfonic porphyrin (D4h symmetry), deuterohemin III (iron deuteroporphyrin III chloride; C2v symmetry), and protohemin III (iron protoporphyrin III chloride; C2v symmetry) in stretched poly(vinyl alcohol) films in the 250-700-nm region. Their linear dichroism was analyzed by using either a "circular absorber" model or a linear absorption oscillator model. For α,β,γ,δ-tetraphenylsulfonic porphyrin with 4-fold symmetry the absorption anisotropy was found to be wavelength independent as for a circular absorber. Deutero- and protohemin III with C2v symmetry had a wavelength-dependent dichroism, indicating the linear type of the allowed transition moments. As expected from theoretical calculation the transitions most affected by peripheral substituents were the relatively weak Q, L, and N bands. Linear dichroism with very similar characteristics was reported earlier by us for native protohemin IX (iron protoporphyrin IX chloride) derivatives (Gryczynski et al. Photochem. Photobiol. 1993, 58, 492). It appears that the absorption of hemes should be considered as a simple combination of linear oscillators. The linear character of heme transition moments is what regulates the radiationless tryptophanheme interactions.
UR - http://www.scopus.com/inward/record.url?scp=0011376371&partnerID=8YFLogxK
U2 - 10.1021/j100086a036
DO - 10.1021/j100086a036
M3 - Article
AN - SCOPUS:0011376371
SN - 0022-3654
VL - 98
SP - 8813
EP - 8816
JO - Journal of Physical Chemistry
JF - Journal of Physical Chemistry
IS - 35
ER -