Four copper complexes of a tridentate Schiff base ligand, 2-pyridyl-N-(2′-methylthiophenyl) methyleneimine, L¹ have been synthesized. All theses species, namely, [L¹Cu₂(SCN)₃]_n (1), [Cu(SCN)(CH₃CN)]_n (3), [(L¹)Cu(N₃)(Cl)] (4) and [(L¹)Cu(N₃)(SCN)] (5) have been structurally characterized. Complex 1 in acetonitrile promotes cycloaddition of a Cu(II) bound SCN⁻ ion to L¹ that exclusively and stoichiometrically forms a mesoionic imidazo[1,5-a]pyridine, namely, 3-(imino-N′-2-methylthiophenyl)imidazo[1,5-a]pyridinium-1-thiolate (2) and a thiocyanato bridged Cu(I) complex, [Cu(SCN)(CH₃CN)]_n (3). The X-ray crystal structure of 1 confirms the presence of square-pyramidal Cu(II) and tetrahedral Cu(I) ions in N₃S₂ and N₂S₂ coordination environments, respectively, bridged to each other viathiocyanate anion. The Cu(II) ions are bonded to a tridentate ligand L¹ and two SCN⁻ ions occupy the remaining equatorial and an axial coordination site to adopt a square-pyramidal coordination geometry. To investigate which SCN⁻ ion, axially or equatorially bound to Cu(II) center, underwent cycloaddition to L¹ to form 2, two mononuclear Cu(II) complexes 4 and 5 have been synthesized and their reactivity towards externally added KSCN was studied. The molecular structures of 4 and 5 feature a meridionally bound L¹ and an azide ion (N₃⁻) in the square plane, while a Cl⁻ or SCN⁻ ion are occupying the axial site, respectively, to fulfill square-pyramidal coordination geometry. Complex 4 reacts with SCN⁻ ion to form 5. That an MeCN solution of 5 itself, or of 5 in the presence of KSCN, does not produce 2, supports that possibly the Cu(II) bound equatorial SCN⁻ ion is responsible for cycloaddition to L¹. Dark purple solid 2 has also been prepared (turnover number ∼4 or 41% yield) efficiently following an alternative and easier one-pot synthesis procedure, that is from a mixture of KSCN and L¹ in the presence of a catalytic amount of anhydrous CuCl₂ (10 mol%) in MeCN in air. The X-ray crystal structure, ¹H NMR spectrum and solution conductivity measurements strongly support that 2 is mesoionic. An MeCN solution of 2 fluoresces at room temperature upon excitation at 240 nm with an emission maximum λ^em at 470 nm, associated with a quantum yield of 0.16 with respect to a standard Rhodamine-6G fluorophore.