Bisamide der Quadrats�ure

Mattes, R.; Johann, G.; Pieper, C.

doi:10.1007/bf00810045

Cited by 5 publications

(2 citation statements)

References 7 publications

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“…There are, however, indications that such compounds are extremely reactive and may be difficult to isolate and CharacterizelQ. .036 (5) . 009141 A3, Dcalc = 1.282 g/cm3).…”

Section: The Planarity Of Squarainesmentioning

confidence: 99%

The molecular and electronic structure of dipiperidinosquaraine

et al. 1985

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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) A. The molecule is located over a center of symmetry, so the four-membered ring (C -C = 1.456(1) A av) is exactly planar; the nitrogen and oxygen atoms are nearly coplanar with the ring, with C -0 = 1.2396(7) and C -N = 1.3112(7) A. Both experimental and theoretical evidence indicates the presence of considerable C -N and C -0 n-bonding, but only a small amount of C -C n-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 x-bonding. Molekulare und elektronische Struktur von DipiperidinoquadratainDipiperidinoquadratain (9) kristallisiert im orthorhombischen Gitter, Raumgruppe Pnab, rnit 4 Molekulen in einer Elementarzelle mit den Abmessungen a = 7.1798(9), b = 9.5362(8) und c = 18.788(2) A. Das Molekul liegt auf einem Symmetriezentrum, d.h. der Vierring (C-C = 1.45611) A) ist genau planar; die Stickstoff-und Sauerstoffatome sind fast mit dem Ring coplanar, mit C -0 = 1.2396(7) und C -N = 1.31 12(7) A. Sowohl die experimentellen als auch die theoretischen Daten zeigen beachtliche C -N-und C -0-x-Bindungen, aber nur eine geringfugige C -C-n-Bindung im Quadratainsystem. Die Berechnungen ergeben starke 1,3-abstoRende Wechselwirkungen im Vierring. Ringfaltung, ein sonst ublicher Mechanismus bei der Vermeidung solcher AbstoRungen, wird hier durch die starke C -N-a-Bindung verhindert.Squaraines -1,3-substituted derivatives of squaric acid -have been known for 20 years l). Various formulations have been used to represent their structures, the most common being l a -c.

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“…There are, however, indications that such compounds are extremely reactive and may be difficult to isolate and CharacterizelQ. .036 (5) . 009141 A3, Dcalc = 1.282 g/cm3).…”

Section: The Planarity Of Squarainesmentioning

confidence: 99%

The molecular and electronic structure of dipiperidinosquaraine

et al. 1985

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“…Both experimental and theoretical evidence indicated the presence of considerable C-X ir-bonding but only a small amount of C-C ir-bonding in the squaraine system.158159 The length of the C-C bonds is hardly influenced by the nature and charge of the substituents, as was substantiated by the diffraction analyses of the squaric amides 213154 In contrast to squaraines, in these amides the exchange of sulfur for oxygen causes a marked alteration of the structural parameters so that for 214 the representation as a cyclobutenedione was considered best, whereas in 213 a bis(thiolate) structure seems to participate considerably in the ground state. 159 Another study determined the crystal structure of the dithallium salt of l,2-bis(cyanimino)cyclobutenedione (215) and of 1,2-diiodocyclobutenedione (216).161 B. Vibrational Analyses Since up to 1987 there was no X-ray diffraction of deltic acid or of a deltate (still not! ), several vibrational analyses and force field calculations were concerned with the structure and bonding of this oxocarbon.…”

Section: B C5 Pseudooxocarbonsmentioning

confidence: 99%