The one-pot reactions between Mn(ClO4)(2) center dot 6H(2)O, Ca(ClO4)(2) center dot 4H(2)O, and the potentially tetradentate (N,O,O,O) chelating/bridging ligand salicylhydroxime (shiH(3)), resulting from the in situ metal ion-assisted amideiminol tautomerism of salicylhydroxamic acid in the presence of various fluorescence carboxylate groups and base NEt3, afford a family of structurally similar {Mn4Ca} clusters with distorted square pyramidal topology. The reported complexes (NHEt3)(2)[Mn4Ca(L-1)(4)(shi)(4)] (1), (NHEt3)(2)[Mn4Ca(L-2)(4)(shi)(4)] (2), (NHEt3)(5)[Mn4Ca(L-2)(4)(shi)(4)(shiH(2))(2)](ClO4) (3), and (NHEt3)(2)[Mn4Ca(L-3)(4)(shi)(4)] (4) contain a similar [Mn4Ca(mu-NO)(4)](10+) core of four Mn-III atoms at the square base and a Ca-II atom occupying the apical site. Peripheral ligation about the core is provided by four eta(1):eta(1):mu carboxylate groups of the anions of 2-naphthoic acid (L1(-)), 9-anthracenecarboxylic acid (L2(-)), and 1-pyrenecarboxylic acid (L3(-)). Solid-state direct current magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the 4 Mn-III centers, which were primarily quantified by using a simple 1-J fit model to give S = 0 spin ground states with low-lying excited states close in energy to the ground state. Solution studies in solvent MeCN were carried out on all complexes and confirmed their structural integrity. Cyclic voltammetry studies showed a similar well-defined reversible oxidation and an irreversible reduction for all complexes, thus establishing their redox potency and electrochemical efficiency. Emission studies in solution proved the optical activity of all compounds, with the observed blue emission peaks attributed to the pi-rich chromophores of the organic fluorescence ligands. The combined results demonstrate the ability of shiH(3) and fluorescence carboxylates to yield new heterometallic Mn/Ca clusters with (i) the same Mn/Ca ratio as the oxygen-evolving complex of Photosystem II, (ii) structural stability in solution, and (iii) a pronounced redox and optical activity.