TY - JOUR AU - Maheut, Géraldine AU - Castaings, Anna AU - Pécaut, Jacques AU - Lawson Daku, Latévi Max AU - Pescitelli, Gennaro AU - Di Bari, Lorenzo AU - Marchon, Jean-Claude TI - Chiroptical and Computational Studies of a Bridled Chiroporphyrin and of Its Nickel(II), Copper(II), and Zinc(II) Complexes PY - 2006 JF - Journal of the American Chemical Society JA - J. Am. Chem. Soc. SN - 0002-7863 VL - 128 IS - 19 SP - 6347 EP - 6356 L1 - http://pubs.acs.org/cgi-bin/article.cgi/jacsat/2006/128/i19/pdf/ja054926o.pdf L2 - http://pubs.acs.org/cgi-bin/article.cgi/jacsat/2006/128/i19/html/ja054926o.html L3 - http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/2006/128/i19/abs/ja054926o.html M3 - 10.1021/ja054926o UR - http://dx.doi.org/10.1021/ja054926o N2 - Circular dichroism (CD) spectra and density functional theory (DFT) calculations are reported for a series of conformationally bistable chiroporphyrins with 8-methylene bridles MBCP-8, which can display either an αααα or an αβαβ orientation of their meso substituents. From DFT geometry optimizations, the most stable form of ZnBCP-8 is found to be the αααα conformer. By passing to NiBCP-8, there is a strong stabilization of the αβαβ conformation with respect to the αααα conformation, consistent with the X-ray structures of αααα-ZnBCP-8 and αβαβ-NiBCP-8. A correlation between the sign of the CD signal in the Soret region and the conformation of the BCP-8 compounds is reported: the αααα conformers H2BCP-8 and ZnBCP-8 show a positive CD signal, whereas the αβαβ conformers NiBCP-8 and CuBCP-8 exhibit a negative signal. The possible contributions to the rotational strengths of αβαβ-NiBCP-8 and αααα-ZnBCP-8, calculated on the basis of their crystal structures, have been analyzed. The CD signals are found to result from a combination of both the inherent chirality of the porphyrin and of extrinsic contributions due to the chiral bridles. These results may have a broad significance for understanding the chiroptical properties of chiral porphyrins and hemoproteins and for monitoring stimuli-responsive, conformationally bistable chiroporphyrin compounds. ID - 864 ER -