Table 4. Comparison of Experimentally Determined (r0) Structural Parameters for Complexes Formed between 5-Membered N-Heterocyclic Rings and H2O.
| Complexa | H-bond donor on het. ringb | r(Hb···N3)/Å | ∠(Hb···N3–C2)/deg | ∠(O–Hb···N3)/deg |
|---|---|---|---|---|
| imidazole···H2O | C–H on C2 | 1.927(27)c | 99.9(41) | 172.1(26) |
| N-methylimidazole···H2O | C–H on C2 | 1.922(4) | 101.0(16) | 177(5) |
| thiazole···H2O | C–H on C2 | 1.977(7) | 95.6(4) | 168.9(1) |
| 5-MT···H2O | C–H on C2 | 2.0037(42) | 99.40(78) | 166.0(23) |
| 2-methylimidazole···H2O | C–CH3 on C2 | 1.923(5) | 116.9(9) | 166.3(28) |
| 4-MT···H2O | C–CH3 on C4 | 2.0296(68)d | 134.7(14)d | 167.4(44)d |
a
Results for imidazole···H2O, N- and 2-methylimidazole···H2O complexes from refs (26 and 27) respectively. Results for thiazole···H2O following reanalysis of results presented in ref (25) (see Table S27).
b
Indicates the atom or group of the heteroaromatic subunit which acts as the hydrogen bond donor in the secondary (weaker) hydrogen bond within the complex.
c
Uncertainties in parentheses are those quoted in the primary source.