In methanol, the reaction of stoichiometric amounts of Mn(OAc) 2 ·4H 2 O and the ligand H 3 hpnbpda [H 3 hpnbpda=N,N′-bis(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine-N,N′-diacetic acid] in the presence of NaOH, afforded a new water soluble dinuclear manganese(II) complex, [Mn 2 (hpnbpda)(μ-OAc)] (1). Similarly, the reaction of Mg(OAc) 2 ·4H 2 O and the ligand H 3 hpnbpda in the presence of NaOH, in methanol, yielded a new water soluble dinuclear magnesium(II) complex, [Mg 2 (hpnbpda)(μ-OAc)(H 2 O) 2 ] (2). DFT calculations have been performed for the structural optimization of complexes 1 and 2. The DFT optimized structure of complex 1 shows that two manganese(II) centers are in a distorted square pyramidal geometry, whereas the DFT optimized structure of complex 2 reveals that two magnesium(II) centers adopt a six-coordinate distorted octahedral geometry. To understand the mode of substrate binding and the mechanistic details of the active site metals in xylose/glucose isomerases (XGI), we have investigated the binding interactions of biologically important monosaccharides d-glucose and d-xylose with complexes 1 and 2, in aqueous alkaline solution by a combined approach of FTIR, UV–vis, fluorescence, and 13 C NMR spectroscopic techniques. Fluorescence spectra show the binding-induced gradual decrease in emission of complexes 1 and 2 accompanied by a significant blue shift upon increasing the concentration of sugar substrates. The binding modes of d-glucose and d-xylose with complex 2 are indicated by their characteristic coordination induced shift (CIS) values in 13 C NMR spectra for C1 and C2 carbon atoms.