Table 1. Calculated IPvert and IPadia of DNA Bases, Base Pairs and DNA Model Systems with phosphates: (5′-G-3′)·(3′-C-5′) and (5′-A-3′)·(3′-T-5′) in electronvolts.
| bases
and base pairs |
DNA models |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| ωb97x/6-31++G(D) |
experimentb |
B3LYP/6-31++G(D) |
M06-2x/6-31++G(D) |
ωb97x/6-31G(D)g |
||||||
| molecule | IPvert | IPadia | IPvert | IPadia | IPvert | IPadia | IPvert | IPadia | IPvert | IPadia |
| guanine (G) | 8.14a (7.86) | 7.71a (7.53) | 8.24 | 7.77 | 7.99a (7.70) | 7.64a (7.46) | 8.10 (7.95) | 7.79 (7.64) | ||
| adenine (A)f | 8.42a (8.27) | 8.16a (7.99) | 8.44 | 8.26 | 8.24a (8.08) | 8.05a (7.87) | 8.50 (8.34) | 8.25 (8.07) | ||
| thymine (T) | 9.13a (8.81) | 8.81a (8.52) | 9.14 | 8.87 | 8.98a (8.65) | 8.74a (8.44) | 9.23 (8.88) | 8.94 (8.61) | ||
| cytosine (C) | 8.86a (8.59) | 8.74a (8.44) | 8.94 | 8.68 | 8.67a (8.40) | 8.56a (8.30) | 8.95 (8.67) | 8.82 (8.53) | ||
| G-C | 7.24 | 6.81 | – | – | 7.06 | 6.72 | 7.33 | 6.91 | 6.90 | 6.30 |
| G-C (PT) | – | 6.86c | – | – | – | 6.76c | – | 6.97c | – | 6.35 |
| A-T | 7.99 (8.01)f | 7.62 | – | – | 7.58 | 7.43 | 8.08 | 7.72 | 7.64 | 7.12 |
| A-T (PT) | – | 7.80c | – | – | – | 7.63c | – | 7.80c | – | 7.26 |
| G•+-C (PT)d | 11.26 | 10.76 | 10.54 | 9.71 | ||||||
| G•+-Ce | 11.67 | 11.26 | 11.48 | 11.13 | 11.77 | 11.34 | 10.97 | 9.92 | ||
| A•+-T (PT)d | 12.67 | 11.50 | – | – | – | – | 12.23 | 11.41 | 11.22 | 10.46 |
| A•+-Te | 11.12 | 10.72 | – | – | 10.91 | 10.69 | 11.23 | 10.81 | 10.41 | 9.34 |
a
Ref (32) and methylated base IPs in parentheses.
c
IPadia calculated with respect to neutral G-C and A-T base pairs.
d
Singlet state.
e
Triplet state.
f
Ref (34). EOM-IP-CCSD/6-311+G(d,p) calculation. IPvert (A) = 8.35 eV.
g
(5′-G-3′)·(3′-C-5′) and (5′-A-3′)·(3′-T-5′). See Figures S23–S28 in the Supporting Information.