Abstract:

Four compounds [M(en)(H₂O)₄]·1,5-nds·(H₂O)₂(M=Ni(1),Co(2),Cd(3),Cu(4), based on ethylene diamine(en) and 1,5-naphthalenedisulfonic acid(nds), were synthesized by hydrothermal synthesis method under room temperature. The structures of the crystals were confirmed by X-ray diffraction(XRD) method and SHELXTL-97 software. The four compounds have the same three dimensional(3D) framework in monoclinic C2/c space group, only different in metal atoms. The cell parameters of compound 1 are:a=1.69026(19) nm, b=1.01373(11) nm, c=1.3448(3) nm, α=90°, β=120.2650°, γ=90°, V=1.9901(5) nm³, Z=4, D_c=1.713 g/cm³, F(000)=1072, R₁=0.0326, wR₂=0.0867. One metal atom is coordinated to four oxygen atoms from water molecules and two nitrogen atoms of one ethylene diamine. There exit abundant hydrogen bonds interactions between free water molecules and oxygen atoms in 1,5-naphthalenedisulfonic acid anion. One dimensional chains were formed through abundant hydrogen bonds and one [Ni(en)(H₂O)₄]²⁺ located between each two nds^2-. The two adjacent [Ni(en)(H₂O)₄]²⁺ arranged by the opposite mode(head to head). The properties of the two compounds were characterized by XRD, thermal gravimetric analysis(TGA), fluorescence spectroscopy and multi-function spectrometer. The molecular recognition properties of compound 3 with M=Cd in methanol solution was studied. The compound 3 was solved in different solvents in which the highest strength of fluorescence spectroscopy occurs in methanol solution. The strength of fluorescence spectroscopy decreases, with increasing concentration of methanol which may have potential applications in fluorescence probe to recognize polarity.

Key words: naphthalenedisulfonic acid, molecular recognition, ethylene diamine, fluorescence