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  • Complexes of Zinc-Coordinated Heteroaromatic N-Oxides with Pyrene: Lewis Acid Effects on the Multicenter Donor–Acceptor Bonding
Title: Complexes of Zinc-Coordinated Heteroaromatic N-Oxides with Pyrene: Lewis Acid Effects on the Multicenter Donor–Acceptor Bonding
4-Nitroquinoline-N-oxide (NQO) and 4-nitropyridine-N-oxide (NPO) are important precursors for the synthesis of substituted heterocycles while NQO is a popular model mutagen and carcinogen broadly used in cancer research; intermolecular interactions are critical for their reactions or functioning in vivo. Herein, the effects of the coordination of N-oxide’s oxygen atom to Lewis acids on multicenter donor–acceptor bonding were explored via a combination of experimental and computational studies of the complexes of NQO and NPO with a typical π-electron donor, pyrene. Coordination with ZnCl2 increased the positive electrostatic potentials on the surfaces of these π-acceptors and lowered the energy of their LUMO. Analogous effects were observed upon the protonation of the N-oxides’ oxygen or bonding with boron trifluoride. The interaction of ZnCl2, NPO, or NQO and pyrene resulted in the formation of dark co-crystals comprising π-stacked Zn-coordinated N-oxides and pyrene similar to that found with protonated or (reported earlier) BF3-bonded N-oxides. Computational studies indicated that the coordination of N-oxides to zinc(II), BF3, or protonation led to the strengthening of the multicenter bonding of the nitro-heterocycle with pyrene, and this effect was related both to the increased electrostatic attraction and molecular–orbital interactions in their complexes.  more » « less
Award ID(s):
2003603
PAR ID:
10532474
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
MDPI
Date Published:
Journal Name:
Molecules
Volume:
29
Issue:
14
ISSN:
1420-3049
Page Range / eLocation ID:
3305
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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