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

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 K(B) approximately 10(8) M(-)(1) and free-energy change of -DeltaG degrees = 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.

Syntheses and Structures of Two Dimethyl Diselenide–Diiodine Adducts and the First Well Characterized Diorgano Disulfide–Nitrosonium Adduct

“…The N-O bond length is 1.1 Å, similar to those of other nitrosonium CT complexes. [20] A trapezoid is formed by the S atoms and NO + with S-N and S-O bond lengths of 2.3 and 2.9 Å, respectively, which are shorter than the sum of the van der Waals radii. [15] The trapezoid is nearly planar (Є S-S-O-N 3.7°).…”

Interaction between some anions and deficient olefinic and aromatic centers

“…The formation of relatively strong complexes together with the distinctive coloration of various anion-p interactions encourages their use in the design of anion-sensing receptors [9][10][11][12][13][14][15][16][17][18][19][20].…”

Multi-signaling detection of Hg2+ and Cu2+ by a ferrocene–pyrazole dyad associated with molecular-scale arithmetic

“…A host capable of multi-center interaction with the guest is often required to ensure maximum selectivity/ sensitivity. Bridged diarenes form very strong (1:1) complexes with cations in which the cation moiety is optimally sandwiched in the cleft between a pair of co-facial aromatic rings which act as a molecular "venus fly trap" [5]. Considering these facts, the molecule R was constructed with phenyl as one of the π-face and cyclopentadienyl (Cp − ) ring of ferrocene as another π-face which are bridged by 1H-pyrazole ring.…”