Normal and twisted intramolecular charge-transfer fluorescence of 4-dimethylaminobenzonitrile in α-cyclodextrine cavities

✍ Scribed by Khader A. Al-Hassan; Uwe K.A. Klein; A. Suwaiyan

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 501 KB
• Volume: 212
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(93)85489-b

✦ Synopsis

Dual fluorescence of 4dimethylaminobenzonitrile (DMABN) has been used to study the behavior of DMABN in a-cyclodextrine (a-CD). Results obtained indicate that DMABN in an aqueous a-CD solution probably exists in three different environmental conditions; polar, slightly polar and hydrophobic. DMABN surrounded by water molecules represents the most polar and least rigid environment. DMABN molecules have two different possible positions inside the CC-CD cavity. The first position could arise when the dimethylamino group of the DMABN molecule is headed towards the larger rim of the a-CD cavity representing the slightly polar and slightly rigid environment. The second position could arise when the dimethylamino group of the DMABN molecule is headed towards the smaller rim ofthe a-CD cavity representing the least polar and most rigid environment. Therefore, it is suggested that the relative positions and contributions of the two fluorescence bands of DMABN in a-CD are determined by restricted molecular motion (controlled by the polarity and free volume of the a-CD cavity) rather than by the polarity alone.