Mechanism of Selfassembly for Riboflavin Tetrabutyrate

Abstract

The transmission and emission spectra of plastic containing Riboflavin tetrabutyrate (RTB) showed that the effect of concentration and thermal gradient on the transannular interaction between th e isoalloxazine (IA) rings could be divided into three clases. The diference in energy between the interacting IA rings and the isolated ring of the S_o s tate were estimated to be nearly the same as the excitation energy for the following vibrational motions, 1. A vibration of III, IV, V, VI of amid absorption band or single bond of t he side-chain lowar than 1450 cm^-1, 2. Combination tone of v ibration of 1V, V or VI o f amid absorption band and skeleton of the IA ring of 2000-2500 cm^-1, 3. A harmonics of the skeletal vibrration of the IA ring, that is, (1500 or 1600 cm^-1) × vibrational quantum number.
Differences in the energy state correspond to the changes in conformation m entioned below. 1. The formation of a contact complex of two IA r ings. 2. The formation of a overlapped dimer at the IA ring. 3. Shortening of the distance between the IA rings to form a tightly overlapped dimer.
These changes in conformation suggest that the tansformation of the RTB molecule with increases in concentration or thermal gradient is due to vibrational excitation at specific bonds.
First, the distance between hydrogen bonds is shortened with increasing c oncentration, which then changes the conformation of the side-chain. At this point, however, the relative orientation of the IA rings is random and unfolded.
As the concentration continues to increase, the IA rings overlap each other and the ring distance becomes shorter.
As the result of the occurrence of thermal gradient in plastic with polymerizaton of methyl methacrylate, step by step the IA rings reach higher levels of skeletal vibration, and the rings become closer and closer.
The charge transfer interaction of the S_o state is promoted by the acceleration of the transannular interaction and RTB at last quenches its emission.