High-resolution structure and conformational dynamics of rigid, cofaciallyaligned porphyrin-bridge-quinone systems as determined by NMR spectroscopyand ab initio simulated annealing calculations
Pm. Iovine et al., High-resolution structure and conformational dynamics of rigid, cofaciallyaligned porphyrin-bridge-quinone systems as determined by NMR spectroscopyand ab initio simulated annealing calculations, J AM CHEM S, 123(24), 2001, pp. 5668-5679
The high-resolution solution structure and dynamics of a cofacially aligned
porphyrin-phenylenequinone compound have been determined using H-1 NMR spe
ctroscopy and simulated annealing calculations. Members of this class of pi
-stacked assemblies feature a 1,8-naphthyl pillaring motif that enforces s
ub van der Waals interplanar separations between juxtaposed porphyryl, arom
atic bridge, and quinonyl components of the donor-spacer-acceptor compound;
this structural motif gives rise to a comprehensive set of structurally si
gnificant NOE signatures that can be used as constraints in quantitative st
ructural calculations. Examination of such data using ab initio simulated a
nnealing analytical methods shows that 5-[8'-(4"-[8"'-(2'"',5"'-benzoquinon
yl)-1"'-naphthyl]-1"-phenyl)-1'-naphthyl]-10,20-diphenylporphyrin displays
an unusual degree of conformational homogeneity in the condensed phase, and
represents a rare example where such an analysis determines unequivocally
a single unique structure in solution.