Singlet, planar

The [S3N3]" cation is of interest as an example of an antiaromatic eight TT-electron system (Section 4.4). Ab initio molecular orbital calculations indicate that a triplet cation, with a planar ring, is more stable than the singlet cation. The [S3N3]" cation has been obtained as the norbomene adduct 5.16, but salts of the free cation have not been isolated. ... 

Compare the geometries of triplet and ground state singlet anthrone. Where do they differ the most Focus on the carbonyl group. Has the CO bond distance altered Does the molecule incorporate a fully-developed CO n bond (as in ground state singlet anthrone), or a single bond (as in phenol) Is the carbonyl carbon planar or puckered Rationalize your observations. 

On the basis of ab initio MO studies on the nitrenium ion 23 derived from 1//-azepine, it has been concluded that the singlet nitrene is a planar, fully conjugated C2v system with substantial 67r-aromatic character. 

Methyl isocyanide, 120 Methyl radical, 10 planar, 65 pyramidal, 66 MethyUunine, 103 Methylazkle, 191 Methylene, 6 singlet, 63 triplet, 62... 

The terminal SS bond (192.2 pm) of S3O is considerably shorter than the central bond (204.0 pm) and represents a double bond the same holds for the SO bond (147.1 pm). The angles SSO (112.1°) and SSS (111.6°) show the expected values. The trans-planar singlet structure is by AH°298=18 kj moG less stable at this level of theory. 

Methanal (formol) presents an additional degree of freedom the out-of-plane wagging of the oxygen atom. In its singlet ground, X Ai, this molecule is planar. But, in its triplet and singlet lowest exited W A" and tt ), this molecule is pyramidal... 

Energy difference between the singlet and triplet states in the planar geometry. The energy difference between the ground state (tub) singlet and the triplet is lOOkJ/mol. 

Di-/-butyl-6-aminothiophenol gives complex (497) under strictly anaerobic conditions. In the presence of air, deep blue-violet solutions are obtained from which mixtures of solid deep blue-black cis/trans-(498) can be isolated.1345 For the square planar Ni complex, the cis-trans isomerization rate is fast. (498) is best described as a singlet diradical due to strong antiferromagnetic coupling of the benzosemiquinonate 7r-radicals.19, 134S... 

---