Experimental and theoretical analysis of vicinal and long-range proton-proton coupling constants for anthracene derivatives.
We studied vicinal and long-range coupling constants for 9-anthracene derivatives, e.g., Br, CN, CHO, NO2, CH2Cl, CH2OH, and OCH3. We performed the accurate measurements using modified J doubling in the frequency domain, even for the smallest couplings immersed within the line width. Density functional theory allowed us to reproduce and exhaustively analyze the physical contributions to the values of these spectroscopic parameters. The theory of atoms in molecules defines a delocalization index that correlates linearly with vicinal and long-range coupling constants when they are grouped in terms of the number of bonds between the coupled nuclei. An exception to this behavior is obtained for 4J(H4,H10) values, which have a negative Fermi contact and the largest delocalization index for each molecule. This observation can be explained by a characteristic "gable roof" arrangement formed by the five nuclei involved in the coupling.
Sánchez-Mendoza
Ernesto
E
Departamento de Bioquímica, Instituto de Química, and Departamento de Física y Química Teórica, Facultad de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, México D. F. 04510, México.
Hernández-Trujillo
Jesús
J
del Río-Portilla
Federico
F
D000873:Anthracenes / Q000737:chemistry*; D011522:Protons; D012997:Solvents / Q000737:chemistry
D000873:Anthracenes; D011522:Protons; D012997:Solvents; C034020:anthracene