Structure of the pyridine-chloranil complex in solution: a surprise from depolarized hyper-Rayleigh scattering measurements.
In this article, we report the structure of a 1:1 charge transfer complex between pyridine (PYR) and chloranil (CHL) in solution (CHCl(3)) from the measurement of hyperpolarizability (β(HRS)) and linear and circular depolarization ratios, D and D', respectively, by the hyper-Rayleigh scattering technique and state-of-the-art quantum chemical calculations. Using linearly (electric field vector along X) and circularly polarized incident light, respectively, we have measured two macroscopic depolarization ratios D = I(X,X)(2ω)/I(X,Z)(2ω) and D' = I(X,C)(2ω)/I(Z,C)(2ω) in the laboratory fixed XYZ frame by detecting the second harmonic (SH) scattered light in a polarization resolved fashion. The stabilization energy and the optical gap calculated through the MP2/cc-pVDZ method using Gaussian09 were not significantly different to distinguish between the cofacial and T-shape structures. Only when the experimentally obtained β(HRS) and the depolarization ratios, D and D', were matched with the theoretically computed values from single and double configuration interaction (SDCI) calculations performed using the ZINDO-SCRF technique, we concluded that the room temperature equilibrium structure of the complex is cofacial. This is in sharp contrast to an earlier theoretical prediction of the T-shape structure of the complex.
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India.
Ravindra
R
Pandey
S
S
Mukhopadhyay
S
S
Ramasesha
Puspendu K
PK
Das
D002703:Chloranil / Q000737:chemistry*; D002725:Chloroform / Q000737:chemistry; D005740:Gases / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry*; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet
D005740:Gases; D011725:Pyridines; D002703:Chloranil; D002725:Chloroform; C023666:pyridine