Cobalt Chemistry with Mixed Aminotroponiminate Salicylaldiminate Ligands: Synthesis, Characterization, and Nitric Oxide Reactivity

A new class of mixed aminotroponimine salicylaldimine ligands and their corresponding cobalt(II) complexes are
reported. This work expands the family of cobalt(II) aminotroponiminato complexes to include salicylaldiminate and
derivatized fluorescein moieties. The H2iPrSATI-n (n = 3, 4) ligands 3 and 4, respectively, contain an aminotroponimine
moiety and a salicylaldimine fragment connected with an alkyl linker. In the H2iPrFATI-n (n = 3, 4) ligands 5 and
6, a derivatized fluorescein replaces the salicylaldimine fragment. The cobalt(II) complexes [Co(iPrSATI-3)] (7) and
[Co2(iPrSATI-4)2] (9) were prepared and structurally characterized. The reaction of NO with both complexes ultimately
results in the formation of a dinitrogen-containing species. The mononitrosyl, [Co(iPrSATI-3)(NO)] (8), was isolated
and characterized. The reactivity of [Co(iPrFATI-3)] (10) and [Co(iPrFATI-4)] (11) with NO mimics that observed for
the salicylaldimine derivatives, as monitored by solution IR spectroscopy. When followed by fluorescence spectroscopy,
reaction of 11 with NO evoked a 3-fold increase in emission intensity after 22 h.