Ion-selective properties of 1,8-bis [2-(dihydroxyphosphinyl)phenoxy]-3,6- dioxaoctane (H4L³), synthesis and vibrational spectra of copper and zinc complexes with H4L³, and crystal and molecular structure of [Cu(H4L³)(H2O) 3][(H2L³)(H2O)]

The ion-selective properties of 1,8-bis[2-(dihydroxyphosphinyl)phenoxy]-3,6-dioxaoctane (H4L3) have been studied and its potentiometric selectivity coefficients have been determined. New complexes [Cu(H4L3)(H2O)3][(H2L3)(H2O)] (I) and Zn(H4L3)(H2L3) · 3H2O, and Cu(H2L3) · 2(H2O) have been synthesized and characterized. The crystal and molecular structure of I has been determined by X-ray crystallography and vibrational spectroscopy. The crystals are monoclinic, a = 10.279(5) Å, b = 26.532(13) Å, c = 8.399(4) Å, β = 99.270(8)°, V = 2260.8(7) Å3, Z = 2, space group Cm, R = 0.0347 for 4325 reflections with I > 2σ(I). Ionic compound I is composed of the [Cu(H4L3)(H2O)3]2+ complex cations and [(H2L3)(H2O)]2− anions. In the cation, the Cu2+ cation located in the m plane is bound to a tetragonal pyramidal (TP) array. The equatorial plane of the TP is formed by two phosphoryl oxygen atoms of the podand (Cu(1)-O, 1.921(2) Å) and two O atoms of two water molecules (av. Cu(1)-O, 1.981(3) Å). The third water molecule is at the axial vertex of the TP at a considerably larger distance (Cu(1)-O, 2.139(3) Å). The anion is of the host-guest type. The host is the deprotonated podand (H2L3)2−, and the guest is the water molecule. The latter is bound to the terminal hydroxyl groups of two phosphoryl groups of the podand by two acceptor hydrogen bonds and to two central ether oxygen atoms of the (H2L3)2− anion by one donor bifurcated hydrogen bond. The cations and anions in the structure are linked by hydrogen bonds to form chains parallel to the c axis.