Structures of C4

✍ Scribed by Robert A. Whiteside; Raghavachari Krishnan; Douglas J. Defrees; John A. Pople; Paul Von R.^Schleyer

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 321 KB
• Volume: 78
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(81)85253-0

✦ Synopsis

Linear (l), cyclic (2) and btcyctic (3) alternatives are considered as posstble ground-state structures for C,. At the h%hest !evels of theory, hlP4SDQ/6-31*//Hr/6-31*, 3, with two T electrons is found to be most stable. A number of polycarbon molecules C, have been detected in graphne vapor [1 ] . Of these, only C, [2] and C3 [3] are well characterized experimentally; both have singlet ground states. C, is linear. For larger values of zz, zt has generally been assumed, following early work of Pitzer and Clementi [4], that C, structures are also linear with 2zz -2 71 electrons. Thus, even values of n correspond to triplet ground states and odd values of n to singlets. A theoretical study of C, by Clement1 [5] indicated that the ground state was a triplet with six zr electrons corresponding to the valence structure 1, :c=c=c=c: 1 The corresponding state syrnznetry is 3X; Less attention has been devoted to possible cyclic structures of C, with singlet ground states *. The Td and D4, forms are high in energy, but the planar polycarbene structures 2 and 3 merit serious attention * Cyclic structures have been examined using the semi-empirical MIND0/2 method [6] However, thus technique falls to give an adequate descrrptton of the states of Ca_