The present article deals with the structurally, spectroscopically and electrochemically characterised osmium-bipyridyl derived complexes [(bpy)₂Os^II(HL₁)Cl]ClO₄ [1]ClO₄ and [(bpy)₂Os^II(HL₂)Cl]ClO₄ [2]ClO₄ incorporating neutral and monodentate pyrazole derivatives (HL) with one free NH function (bpy = 2,2′-bipyridine, HL₁ = pyrazole, HL₂ = 3,5-dimethylpyrazole). The crystal structures of [1]ClO₄ and [2]ClO₄ reveal intramolecular hydrogen bonding interactions between the free NH proton of HL and the equatorially placed Cl⁻ ligand (N–H⋯Cl) with donor–acceptor distances of 3.114(7) Å and 3.153(6) Å as well as intermolecular hydrogen bonding interactions between the NH proton and one of the oxygen atoms of ClO₄⁻ (N–H⋯O) with donor–acceptor distances of 2.870(10) Å and 3.024(8) Å, respectively. The effect of hydrogen bonding interactions has translated into the less acidic nature of the NH proton of the coordinated HL with estimated pK_a > 12. 1⁺ and 2⁺ exhibit reversible Os(II)/(III) and irreversible Os(III)/(IV) processes in CH₃CN within ±2.0 V versus SCE. The effect of 3,5-dimethyl substituted HL₂ on 2⁺ has been reflected in the appreciable lowering (40 mV) of the Os^II/III potential, along with the further decrease in the acidity of the NH proton (pK_a > 13.0) with regard to HL₁ coordinated 1⁺ (pK_a: ∼12.3). The electronic spectral features of Os(II) (1⁺/2⁺) and electrochemically generated Os(III) (1²⁺/2²⁺) derived complexes have been analysed by TD-DFT calculations. The efficacy of the 1⁺ and 2⁺ encompassing free NH proton towards the anion recognition process has been evaluated by different experimental investigations using a wide variety of anions. It however establishes that receptor 1⁺ can recognise both F⁻ and OAc⁻ in acetonitrile solution, while 2⁺ is exclusively selective for the F⁻ ion.