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The molecular and electronic structure of dipiperidinosquaraine
Author(s) -
Budzelaar Peter H. M.,
Dietrich Hans,
Macheleid Jürgen,
Weiss Robert,
von Ragué Schleyer Paul
Publication year - 1985
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19851180531
Subject(s) - chemistry , orthorhombic crystal system , crystallography , ring (chemistry) , stereochemistry , molecule , crystal structure , organic chemistry
Dipiperidinosquaraine ( 9 ) crystallizes in the orthorhombic system, space group Pnab , with four molecules in a cell of dimensions a = 7.1798(9), b = 9.5362(8), and c = 18.788(2) Å. The molecule is located over a center of symmetry, so the four‐membered ring (C – C = 1.456(1) Å av) is exactly planar; the nitrogen and oxygen atoms are nearly coplanar with the ring, with C O = 1.2396(7) and C N = 1.3112(7) Å. Both experimental and theoretical evidence indicates the presence of considerable C N and C O π‐bonding, but only a small amount of C C π‐bonding in the squaraine system. The calculations indicate the presence of strong 1,3‐repulsive interactions within the four‐membered ring. Ring puckering, which is a common mechanism to alleviate these repulsions, is prevented here by the extensive C N π‐bonding.