A new definition of Dewar-type resonance energies

A molecular clip with allosteric binding properties

“…Allosteric effects play an important role in regulating biological processes like oxygen transport and enzyme activity.1 There are only a few reports in literature on synthetic receptors in which binding is regulated by the allosteric effect. Most of these reports concern hosts with binding sites for metal ions.2 Very recently, Schneider and Ruf have described a synthetic receptor which shows enhanced binding of aromatic substrates in the presence of C u 2+ or Z n 2+, due to an allosteric effect.3 W e report herein a molecular receptor ( 1), that can exist in different conformations, one of which is able to bind 1,3-dinitrobenzene by tt-tt interactions. Moreover, we describe a bis-crown ether analogue of this receptor (2) in which a dinitrobenzene-binding conformation can be induced by addition of a metal salt (Figure la).…”

“…This process could be monitored with a two-dimensional *H N M R exchange experiment.4 Inspection of C P K models and molecular (1) Since the aa conformer of 2 is expected to display the highest affinity for 1,3-dinitrobenzene, we were tempted to assess the ability of metal ions to induce substrate binding by an allosteric …”

Chemistry-Relevant Isospectral Graphs. Acyclic Conjugated Polyenes

“…As a matter of fact, QG(x) is essentially equivalent to the later-proposed matching polynomial, [29][30][31] …”

Aromatic molecular zones and fragments

“…In the quantitative evaluation of aromaticity, experimentally determined or theoretically calculated, parameters currently used include: magnetic properties, 2-12 geometry, [13][14][15][16][17][18] bond orders, [19][20][21][22][23][24][25][26][27][28] isodesmic energy, 29 combustion energy, 30 (topological) resonance energy, [31][32][33][34][35][36][37][38] bond lengths [40][41][42][43][44][45][46] etc.…”

“…[33][34][35] Almost simultaneously, "topological resonance energy" TRE was put forward by Aihara 31 and Gutman et al 32 The values of aromaticity (Randić) and TRE (Gutman) are computed using very different formulas. These two models, used in the quantitative computation of aromaticity, use the "limit" Kekulé structures, in fact non-existent.…”