Title

Molecular Recognition of NO/NO+ via Multicenter (Charge-Transfer) Binding to Bridged Diarene Donors. Effect of Structure on the Optical Transitions and Complexation Thermodynamics

Document Type

Article

Language

eng

Publication Date

2003

Publisher

American Chemical Society

Source Publication

The Journal of Organic Chemistry

Source ISSN

0003-2670

Abstract

Bridged diarenes form very strong [1:1] complexes with nitrosonium/nitric oxide in which the NO moiety is optimally sandwiched in the cleft between a pair of cofacial aromatic rings which act as a molecular “Venus flytrap”. The spectral features of these associates are generally similar to those for [1:1] and [2:1] nitrosonium complexes with mononuclear alkyl-substituted benzenes, and they are appropriately described within the LCAO molecular-orbital methodology and the Mulliken (charge-transfer) formulation of donor/acceptor electronic transitions. The thermodynamics study indicates that the efficient binding is determined by (i) the close matching of the donor/acceptor redox potentials and (ii) the ability of bridged diarenes for multicentered interactions with a single NO moiety. The best fit of the electronic and structural parameters is provided by a calixarene host that allows the interacting centers to be arranged in a manner similar to those extant in [2:1] nitrosonium complexes with analogous (nonbridged) aromatic donors; this results in its very strong noncovalent binding with nitrosonium/nitric oxide with the formation constant of KB ≈ 108 M-1 and free-energy change of −ΔG° = 45 kJ mol-1. Such strong, selective, and reversible bindings of nitrosonium/nitric oxide by (cofacial) aromatic centers thus provide the basis for the development of efficient NO sensors/absorbents and also suggest their potential relevance to biochemical systems.

Comments

The Journal of Organic Chemistry, Vol. 68, No. 10 (2003): 3947-3957. DOI.

Sergey V. Lindeman and Rajendra Rathore were affiliated with the University of Houston at the time of publication.

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