Sayed M, Biedermann F, Uzunova VD, Assaf KI, Bhasikuttan AC, Pal H, Nau WM, Mohanty J. Triple emission from p-dimethylaminobenzonitrile-cucurbit[8]uril triggers the elusive excimer emission.
Chemistry 2014;
21:691-6. [PMID:
25393034 DOI:
10.1002/chem.201404902]
[Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Indexed: 11/08/2022]
Abstract
The intriguing dual-emission behavior of p- dimethylaminobenzonitrile (DMABN) and the identity of the associated excited states is, arguably, the most extensively investigated and also controversially discussed molecule- specific phenomenon of modern photochemistry. We have now found a new, third fluorescence band when DMABN is encapsulated within the water-soluble molecular container cucurbit[8]uril (CB8). It is centered between the previously observed emissions and assigned to the elusive excimer emission from DMABN through 1:2 CB8:DMABN complex formation. Heating of the CB8⋅(DMABN)2 complex from 0 to 100 °C results in the dissociation of the ternary complex and restoration of the dual-emission properties of the monomer. Alternatively, monomer emission can be obtained by selecting cucurbit[7]uril (CB7), a host homologue that is too small to accommodate two DMABN molecules, or by introducing ethyl instead of methyl groups at the amino terminus of the aminobenzonitrile guest.
Collapse