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

Table 5

Assignment of the measured Ar-matrix frequencies (cm⁻¹).

Exp.	Approximate description ^(a)	Exp.	Approximate description ^(a)
3566.2–3563.0	νOH H01	1353.9	δC–OH K04
3514.5	νNH	1338.5	δC–OH H01
3498.7	νOH H01	1333.5	δC–OH H01
		1332.0	δC–OH H01
3371.0	νOH K02 K03 K04 K06	1309.5
2931	νCH	1289.4	νRing/δ ipCH/δ ipC–OH
1796.4	νC=O K07 K09	1275	νRing/δ ipCH
		1233.5−1232.9	νRing
1721.0	νC=O K02 K03 K04 K06
1716.4	νC=O H01	1212.8	νRing
1713.7		1187–1181	δ ipCH
1690.0	νRing	1169–1163
1619.0	νRing	1155.7	νC–OH H01
1610.8	νC=C H01	1149.8	δ ipCH
1602.0		1135	νRing/νC–OH/δ ipC– OH
1598.3	νRing/δ ipCH	1132.1	νC–OH H01
1590.3	νRing/δ ipCH	1112.2	νC–OH K02 K03 K04
1535.0	νRing	1103.7
1523.0		1097.6	δ ipCH/δ ipNH/νRing
1492.8	δ ipCH/νRing	1093.0	δ ipCH/νC–OH
1460.0	νRing/δ ipNH/δ ipCH	1044	δ ipRing
1457.8	δ ipNH	1044	δ ipRing
1444.6	δ ipNH	1055.1–1052.4
1427.6	δ ipCH/νC–OH H01	1033.5	δ ipdef ^(b)
1421	δ ipCH/νC–OH
1412.9	δ ipCH/νC–OH H01
1408.8	νRing/δ ipC–OH	1013.2	δ ipCH
		866.2	δ ipdef ^(b)
1378	νRing	768.2	δ opRing
1368.1	δC–OH K03	757.5	δ ipCH
1361.4	δC–OH K02	752	δ ipRing
1358.8	δC–OH K06 K07 K09	739.9	δ opdef ^(b)
		656	δ ipRing/δ ipdef ^(b)
		604	δ ipRing/δ ipdef ^(b)
		514	δ ipRing
		418.5	δ opNH

^(a)see text for details.
^(b) in-plane or out-of-plane molecular deformation.