Design of Brønsted Neutral Organic Bases and Superbases by Computational DFT Methods: Cyclic and Polycyclic Quinones and [3]Carbonylradialenes

Abstract

The gas‐phase proton affinities and basicities of a large number of extended polycyclic π systems possessing a carbonyl oxygen head serving as a basic proton scavenger are explored by using DFT at the B3LYP/6‐311+G(d,p)//B3LYP/6‐31+G(d) level of theory. Some of these neutral organicsuperbases exhibit proton affinities in the range of 264–284 kcal mol–1. In constructing these systems it turned out that a =C(NMe2)2 fragment attached to a quinoid six‐membered ring enhanced the basicity to a considerable extent. There is abundant and convincing evidence that protonation triggers strong aromatization of the quinoid rings. Moreover, sequential quinoid rings undergo the aromatic domino effect upon protonation if linearly aligned. Triadic analysis has revealed that highly pronounced basicity in some studied systems is a result of the synergistic action of Koopmans' frozen neutral base ionization energy contribution and subsequent relaxation of the radical cation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Engineering exceptionally strong oxygen superbases with 1,8-diazanaphthalene di-N-oxides

“…The favorable influence of multiple hydrogen bonds on enhancing the basicity (and acidity) of simple organic amines and alcohols has recently been particularly emphasized by Bachrach 15 and Kass. 16 Basic centers are usually nitrogen moieties due to their strongly attractive interactions with protons, since nitrogen lone pair orbitals are energetically higher-lying compared to, for example, those of oxygen in ethers and ketones, 17 in line with reports that ketones 18 and aldehydes 19 are less basic than the corresponding imines. 20 Yet, herein we wish to demonstrate that the oxygen basicity of N-oxides surpasses that of the related nitrogen compounds and that molecules containing two neighboring N-oxide moieties are several orders of magnitude stronger bases than the analogous nitrogen proton sponges, approaching a gas-phase proton affinity of 300 kcal mol À1 , proposed as a borderline between superbases and hyperbases.…”

Design of Robust Organosuperbases and Anion Receptors by Combination of Azine Heterocycle Skeleton and Phosphazene Motif

“…Recent advances in computational chemistry show its extensive application in the design of superacids and superbases, which makes them reliable counterparts in the experimental research . The calculations of the gas phase proton affinity (PA) and basicity (GB) using Density Functional Theory (DFT) method are very cost effective and reliable.…”

Design of Exceptional Strong Organosuperbases Based on Iminophosphorane and Azaphosphiridine Derivatives: Harnessing Ring Strain and Aromaticity to Engineer Neutral Superbases

“…Based on these factors, a wide variety of the superbase such as silylenes, germylenes, guanidines, imidazolines, guanidinophosphazenes, phosphorus ylides, amines, quinones, iminopolyenes, etc . have been reported in the scientific resources . Phosphazenes are a large family of the phosphorous superbases which have nowadays attracted much attention .…”