C5 molecule: Structure and infrared frequencies

Isotopic Study of New Fundamentals and Combination Bands of Linear C5, C7, and C9 in Solid Ar

“…As expected, the absorptions labeled B and C correspond to the 13-12-12-12-12 and 12-13-12-12-12 Table 3. Comparison of Observed Vibrational Frequencies (cm -1 ) of the (ν 1 þ ν 4 ) Combination Band for Single 13 …”

“…Using the frequency of the previously assigned 15 ν 4 (σ u þ ) fundamental at 1446.6 cm -1 in eq 1 gives a frequency of 1946 cm -1 for the symmetric stretching mode ν 1 (σ g þ ) of linear C 5 . Figure 3a shows the spectrum to the low frequency side of the absorption at 3471.8 cm -1 obtained using a carbon rod with 10% 13 C enrichment. For comparison, Figure 3b shows the identical region of the spectrum obtained using a 12 C rod.…”

A combination band at 1699.8 cm−1 for C4 trapped in Ar

“…Based on detailed 13C data for seven isotopomers and the results of ab initio calculations by Michalska et al 11 and h · . 1819 ot er lllvestlgators, , the FTIR experiments have proved that an absorption band at 1543.4 cm -1, which had previously been assigned to the 11" C=C stretching vibration of linear C S , 20,21 actually belongs to the 11 2 , C=C stretching vibration of the C 4 chain. However, in a recent EPR study22 in this laboratory of C 4 trapped in Ar, evidence was found from splittings in the line profiles that the carbon tetramer is not strictly linear, but is either trans-or cis-bent.…”

Is the C8ring nonplanar?

“…have received considerable research attention for more than two decades [1]. Nevertheless, the interest has recently become even stronger in both computations [2][3][4][5][6][7][8][9][10][11][12][13] and observations [14][15][16][17][18][19][20][21] in an apparent connection with the large carbon spheroidal molecules [22]. The computational studies [1] mostly predict linear arrangements for odd-numbered small carbon aggregates, while with the even species two isomers are suggested, planar cyclic and linear (triplet electronic state).…”