Combined FTIR Matrix Isolation and Density Functional Studies of Indole-3-Pyruvic Acid Molecule. Spectroscopic Evidence of Gas-Phase Tautomerism

Table 2

OH and NH, C=O, and C=C -scaled B3LYP/6-311++G** stretching frequencies (cm⁻¹) of the most abundant gas-phase species.

Tautomer	OH	NH	C=O	C=C
K02	3418	3523	1780–1712
H01	3551	3518	1684	1610
	3477
K03	3423	3523	1782–1708
K04	3417	3527	1785–1728
K06	3421	3526	1787–1713
K07	3523	3525	1744–1738
K09	3522	3524	1740–1737
H05	3571	3518	1734	1601
	3560