Heteronuclear, mixed-metal Ag(i)–Mn(ii) coordination polymers with bridging N-pyridinylisonicotinohydrazide ligands: synthesis, crystal structures, magnetic and photoluminescence properties

Abstract

Mixed-metal dicyanoargentate-bridged coordination polymers of Ag(I)–Mn(II) have been prepared and their structure and magnetic properties were determined. Reaction of manganese(II) chloride and potassium dicyanoargentate(I) with (X)(pyridin-2-ylmethylene)isonicotinohydrazide ligands (HL¹ X = Ph, HL² X = Me, HL³ X = H) produced the coordination polymer 2D-[Mn(μ-L¹)(Cl)(μ-NCAgCN)Mn_0.5(CH₃OH)]_n (1), 1D-{[Mn(L²)(Cl)(μ-NCAgCN)Mn_0.5(CH₃OH)]CH₃OH}_n (2) and [Mn(L³)(Cl)(μ-NCAgCN)Mn_0.5(CH₃OH)]_n (3) in good yields. Trinuclear {Mn(μ-L¹)Mn(μ-L¹)Mn} and [Ag(CN)₂]⁻ building units form a two-dimensional slab in 1 and 1D strands in 2. Variable temperature magnetic susceptibility measurements showed that despite the long distance among the high spin Mn(II) ions [10.4676(12) Å and 10.522(1) Å, for 1 and 2, respectively], weak antiferromagnetic coupling takes place through the long NC–Ag–CN bridge. The best fit parameters to the model led to the magnetic coupling constant of J = −0.1 and J = −0.47 cm⁻¹ for 1 and 2, respectively. The photoluminescence behaviour of compounds 1 and 2 was studied. The spectrum of compound 1 shows a broad emission centered at about 450 nm and two excitation maxima at 270 and 310 nm.