Title

Complexes of acridine and 9-chloroacridine with I2: formation of unusual I6 chains through charge-transfer interactions involving amphoteric I2

ACS Citation

Rimmer, E. L.; Bailey, R. D.; Hanks, T. W.; Pennington, W. T. Complexes of acridine and 9-chloroacridine with I2: formation of unusual I6 chains through charge-transfer interactions involving amphoteric I2. Chemistry 2000, 6, 4071-81.

Abstract

Acridine and 9-chloroacridine form charge-transfer complexes with iodine in which the nitrogen-bound I2 molecule is amphoteric; one end serves as a Lewis acid to the heterocyclic donor, while the other end acts as a Lewis base to a second I2 molecule that bridges two acridine.I2 units. In the acridine derivative (acridine.I2)2.I2, 1], the dimer has a "zigzag" conformation, while in the 9-chloroacridine derivative (9-Cl-acridine.I2)2.I2, 2], the dimer is "C-shaped". The thermal decomposition of the two complexes is very different. Compound 1 loses one molecule of I2 to form an acridine.I2 intermediate, which has not been isolated. Further decomposition gives acridine as the form II polymorph, exclusively. Decomposition of 2 involves the loss of two molecules of I2 to form a relatively stable intermediate (9-Cl-acridine)2.I2, 3]. Compound 3 consists of two 9-Cl-acridine molecules bridged through N...I charge-transfer interactions by a single I2 molecule. This compound represents the first known example, in which both ends of an I2 molecule form interactions in a complex that is not stabilized by the extended interactions of an infinite chain structure. The ability of the terminal iodine of an N-bound I2 to act either as an electron donor (complexes 1 and 2) or as an electron acceptor (complex 3) can be understood through a quantum mechanical analysis of the systems. Both electrostatic interactions and the overlap of frontier molecular orbitals contribute to the observed behavior.

Source Name

Chemistry (Weinheim an der Bergstrasse, Germany)

Publication Date

1-1-2000

Volume

6

Issue

22

Page(s)

180-182

Document Type

Citation

Citation Type

Article