Journal of Spectroscopy

Guanine: A Combined Study Using Vibrational Spectroscopy and Theoretical Methods

Table 2

Experimental and calculated wavenumbers for anhydrous guanine.


Experimental			Calculated		Approximate description^[c]
INS	Raman	FT-IR	Scaled G03W^[a]	PW^[b]	Approximate description^[c]

30				40 46 51 71	External mode
60	75			73 76 85 90	External mode
90	107			100 109 109 110	External mode
127	124 138			112 130 139 149	External mode
127	124 138			112 130 139 149	External mode
158	161		147	153 167 172 178	External mode + Ring “butterfly”
177				178 180 182 185	Ring “butterfly”
196	203		157	190 197 197 200	Ring “butterfly”
238	245		196	246 249 261 262	Γ(C2–N1–C6)
333	341		301	343 344 361 370	(C6–C5–N7) – (N3–C4–N9); δ(C=O)
361 379	360		376	379 381 381 382	Γ(Pyr) + Γ(Im): N7 + N9−N3
403	397		336	406 407 421 427	(N2–C2−Ν1) + (N1–C6=O); H-bond effect
499	494	503	488	494 506 512 519	(N1–C6–C5) + (C2–N3–C4); (N3–C2–C1) + (C4–C5–C6)
507					(N1–C6–C5) + (C2–N3–C4); (N3–C2–C1) + (C4–C5–C6)
551 570	546 562	540 557	540	538 542 560 563	(C2–N1–C6) + (N3–C4–C5)
601	601	604	651	614 615 615 616	Γ(C8–N7–C5) – Γ(C4–N9–C8)
657	650	644	635	643 647 648 649	Pyr + Im ring breathing
694	692	688	694	689 691 692 695	C4-C6 umbrella; γ(N2-H10)
705 737	711 727	702 727	676	692 698 717 727 732 732 734 735	(N2–C2–N1) – (N1–C6=O); (C5–C4–N9) + (C6–C5–N7
786	775	779	615 706	701 710 712 712	ω(NH₂); C2 umbrella
802	803	791		807 810 813 819	τ(NH₂); γ(C8–H)
802	803	791	741	785 786 787 788	C4 + C6-C5 umbrella; τ(NH₂)
847	848	850	803	831 832 842 844	(C4–N9–C8) + (N1–C2–N3) – (N2–C2–N3)
886 909	878	881	497 594 821 334	830 830 836 841 900 900 907 908 994 994 994 995	γ(C8–H); γ(N7–H); γ(N1–H); t(NH₂)
946	935	949	921	935 937 950 952	(N7–C8–N9)
1045	1046	1043	998	1046 1051 1063 1065	ν(C2–N1) + ν(C2–N2) + ν(C2–N3)
1109 1121		1120	1050 1071	1120 1121 1124 1130	δ(C8–H) – δ(N7–H); t(NH₂) ν(C4–N9) + ν(C4–N3) – ν(C5–N7) – ν(C6–N1)
1160	1158	1173	1115	1155 1158 1160 1174	t(NH₂); δ(C8-H)
1178 1190	1185	1173	1150	1191 1197 1200 1201	ν(C6–N1) – ν(C8–N7); ν(C4– N9) + ν(C4–N3); δ(C8–H)
1226	1232	1215	1277	1229 1234 1249 1250	ν(C8–N7) + ν(C8–N9) – ν(C6–N1) – ν(C5–N7); δ(N1–H)
1269	1265	1261	1245	1274 1275 1280 1281	ν(N9–C8) + ν(C5–C6) – ν(C4–N9) − ν(C6–N1); δ(C8–H)
1375 1406	1359 1390	1373	1334 1355	1379 1380 1382 1384 1386 1391 1394 1395	ν(C4–N3) + ν(C5–C6) + ν(C4–C5) + ν(C2–N1) – ν(C4-N9) – ν(C5–N7) – ν(C8–N9)
1417	1421	1417	1414 1438	1441 1441 1447 1447	δ(N1–H); ν(C2–N2) + ν(C5–C6) – ν(C8–N9)
1463	1466	1465	1504	1460 1460 1463 1473	ν(C8–N9) + ν(C2–N1) + ν(C6–N1) – ν(C8–N7) – ν(C2–N3); δ(C8–H)
1482	1479	1475	1522	1482 1483 1487 1491	ν(C8–N7) – ν(C5–N7); δ(N7–H)
1550	1549	1552 1562	1617	1526 1541 1545 1549 1560 1560 15631567	α(NH₂); ν(C8–N9) + ν(C4–N9) + ν(C=O) + ν(C2–N2); ν(N3–C4) – ν(C4–C5) – ν(N3–C2); δ(N1–H)
1613	1598	1637	1570	1597 1597 1620 1622	α(NH₂) + δ(N1–H); ν(C4–N3); ν(C5–C6)
1670 1687	1674	1672 1697	1742	1657 1662 1668 1670 1671 1684 1685 1706	α(NH₂); ν(C2–N1) + ν(C2– N3) + ν(C5–C6) – ν(C=O) – ν(C2– N2); δ(N1–H)

	2708	2696			Combination mode
	2898	2846 2904	3472	2556 2556 2630 2644	ν(N1–H)
	2992	2989	3531	2854 2854 2871 2919	ν(N7–H)
		3064
	3110	3113	3435	2991 2991 3035 3043	ν(NH₂)
	3164	3178
	3348	3325	3139	3132 3132 31333134	ν(C8–H)
			3536	3166 3167 31733177	ν(NH₂)

[a]At the DFT B3LYP/6-31G** level of theory. The calculated vibrational modes were scaled accordingly to [28]. [b]Using the LDA functional and Plane-Wave methodology, unscaled. [c]According to the PW description. The “+” and “–” signals represent vibrations occurring simultaneously in the same direction or in opposite directions, respectively. ω: wagging; δ: in-plane deformation; : in-plane ring deformation of skeletal atoms; γ: out-of-plane deformation; Γ: out-of-plane ring deformation of skeletal atoms (umbrella mode); α: scissoring; τ: torsion; t: twisting; ν _s: symmetric stretching; ν _a: antisymmetric stretching.