Table 2. Non-Bonded Interactions Observed between 5-FU Molecule and Silica Surfacesa.
| Groups
on the surfaces showing interaction |
||||||||
|---|---|---|---|---|---|---|---|---|
| Groups on 5-FU showing interaction | MCM-41 | MCM-CN | MCM-CH3 | MCM-NH2 | MCM-NH3+ | MCM-COOH | MCM-COO- | |
| H-Bond Interactions | ||||||||
| 5-FU | ||||||||
| Acceptor | 2(C=O) | H–O–Si | H–O–Si | H–O–Si | H–O–Si, NH2–(C3H6)–Si | H–O–Si | with two H–O–Si groups | – |
| 4(C=O) | – | H–O–Si | – | – | H–O–Si | – | H–O–Si | |
| Donor | 3(N–H) | Si–O–H | Si–O–H | – | – | Si–O–H | Si–O–H, Si–O–Si | –OOC–(C3H6)–Si |
| 5-FU1 | ||||||||
| Acceptor | 2(C=O) | H–O–Si | H–O–Si | H–O–Si | H–O–Si | H–O–Si, NH3+–(C3H6)–Si | H–O–Si | – |
| 4(C=O) | H–O–Si | H–O–Si | – | – | H–O–Si | H–O–Si | – | |
| 1(N–) | – | – | – | NH2–(C3H6)–Si | – | – | – | |
| Donor | 3(N–H) | Si–O–H | Si–O–H | – | Si–O–H | Si–O–H | Si–O–H | – |
| 5-FU2 | ||||||||
| Acceptor | 2(C=O) | H–O–Si | H–O–Si | H–O–Si | H–O–Si | H–O–Si | – | – |
| 4(C=O) | – | – | – | – | – | H–O–Si | – | |
| 3(N–) | – | – | – | NH2-(C3H6)–Si | – | H–O–Si | – | |
| Donor | 1(N–H) | Si–O–H | – | – | Si–O–H | Si–O–H, Si–O–Si | – | – |
| Hydrophobic Interactions | ||||||||
| 5-FU, | ring carbons | Si, Si–O–Si | CN–(C3H6)–Si, | CH3–(C3H6)–, | NH2–(C3H6)–Si | NH3+–(C3H6)–Si, | HOOC–(C3H6)–Si, | –OOC–(C3H6)–Si |
| 5-FU1, | Si–O–Si, Si | Si–O–Si | Si–O–Si, Si | No interactions with ionized species of 5-FU | ||||
| 5-FU2 | ||||||||
| Adsorption Energy (kcal/mol) | ||||||||
| Molecular Mechanics (MM) by OPLS3 force field | ||||||||
| 5-FU | –14.318 | –20.227 | –12.736 | –15.320 | –12.839 | –16.057 | –20.286 | |
| 5-FU1 | –26.629 | –39.083 | –22.507 | –33.885 | –226.971 | –32.143 | 110.357 | |
| 5-FU2 | –19.483 | –28.497 | –19.329 | –23.796 | –234.593 | –32.557 | 99.735 | |
| Quantum Mechanics (QM) by Jaguar | ||||||||
| 5-FU | –17.026 | –28.160 | –13.986 | –18.331 | –23.810 | –19.755 | –12.544 | |
| 5-FU1 | –64.856 | –68.944 | –41.854 | –66.856 | –249.845 | –61.227 | 64.081 | |
| 5-FU2 | –31.844 | –48.319 | –55.653 | –42.433 | –253.184 | –44.096 | –41.804 | |
| Actual % loading from literature report16 | 18.34 | 22.54 | 12.73 | 28.89 | – | 20.73 | – | |
a
The numbers in bold outside brackets represent the position of the atom in the 5-FU molecule, the underline below the groups represents the groups involved in interaction.