Table 4: The UV-Vis data and their assignments for L1, L2 and their complexes.
| Compound | UV-Vis data (nm) | Assignment | ||
| π–π∗ | n–π∗ | d−d/CT | ||
| L1 | 258 | 325 | — | — |
| Fe (1) | 269 | 349 | — | — |
| Ni (2) | 260 | 333 | — | — |
| Cu (3) | 264 | 314 | 368 | CT |
| L2 | 275 | 365 | — | — |
| Fe (4) | 258 | 348 | 439 | CT |
| Ni (5) | 259 | 339 | 431 | 1A2g ← 1A1g |
| Cu (6) | 285 | 334 | 441 | 2B2g ← 2B1g |