Vibrational Fingerprint of Erlotinib: FTIR, RS, and DFT Studies

Table 3

Calculated (PCM model) and experimental wavenumbers for the RS spectra of erlotinib in the solution (pH 7).

Calculated wavenumbers (cm^−1)	Assignment^a	Experimental wavenumbers (cm^−1)
	B3LYP/6-311G(d, p) (PED > 5%)	Literature [9, 37–42]	RS
2184	ν(C≡C)		2108
1606	ν(CC)Phe, ρb(NH), ν(C=N)Q, ν(CC)Q	ν(CC)Q	1594
1541	ρb(NH), ν(NC)Q-NH, ν(CN)Q, ν(C=N)Q, ρb(CH)Phe, ν(CC)Q	ν(Phe), ρb(NH)	1539
1517	ν(CC)Q, ρs(CH2)OCH2, ρs(CH2)CH3		1513
1440	ν(CC)Phe, ρb(CH)Phe, ν(NC)Q-NH,	ρb(NH), ν(Phe)	1433
1399	ν(C=N)Q, ν(CC)Q, ρb(CH)Q, ρb(NH)	ν(Q), ρb(NH), ρb(CH)	1394
1355	ρb(CH)Q, ν(CC)Q, ρb(CH)Phe		1357
1346	ρw(CH2)CH2O, ρw(CH2)OCH2, ρw(CH3), ν(CC)Q, ν(CN)Q,		1345
1298	ρb(CH)Phe, ν(CC)Phe, ρw(CH2)CH2O, ρw(CH2)OCH2, ρb(CH)Phe-Q, ν(CC)Q, ν(NC)Q	ν(CN)	1280
1266	ρt(CH2)OCH2, ρt(CH2)CH2O, ρb(CH)Phe-Q, ν(CC)Q, ν(NC)Q, ρb(CH)Phe, ν(CC)Phe	ρb(CH), ρb(NH), ν(CN)	1246
1240	ρw(CH2)CH3, ρt(CH2)CH3, ν(CO)CH2O, ρw(CH2)CH2O, ρb(CH)Phe, ρb(CH)Q		1230
1144	ρb(CH)Phe, ρb(CH)Phe-Q, ρw(CH2)CH3		1147
998	δ(Phe)	δ(Phe)	996
703	δoop(Phe-Q), δ(PYMD-Q), δ(CQOC), ρb(CH)Phe,δ(Phe), ρs(CH2)CH2O, ρs(CH2)OCH2		702

^aAbbreviations: ν, stretching; ρ_b, bending; ρ_w, wagging; ρ_s, scissoring; δ, deformation; as, antisymmetric; oop, out-of-plane; Phe, phenyl ring; Q, quinazoline group.