Syntheses, structures and some electrochemistry of Cu(II) complexes with tris[(2-pyridyl)methyl]amine: [Cu{N(CH2-py)3}(N3)]ClO4 (I), [Cu{N(CH2-py)3}(O–NO)]ClO4 (II) and [Cu{N(CH2-py)3}(NCS)]ClO4 (III)

Compounds derived from tris[(2-pyridyl)methyl]amine, having composition [Cu{N(CH2-py)3}(N3)]ClO4 (I), [Cu{N(CH2-py)3}(O–NO)]ClO4 (II) and [Cu{N(CH2-py)3}(NCS)]ClO4 (III) were prepared and characterized by several techniques, including the X-ray determination of the structures of (I) and (II). The complex [Cu{N(CH2-py)3}(N3)]ClO4 (I) crystallizes in the monoclinic, space group P21/c (No. 14) with a=15.253(3), b=9.036(2), c=14.990(3) Å, β=94.79(3)°, V=2058.9(7) Å3, Z=4; Dcalc=1.598 mg/m3. The cation is distorted from trigonal bipyramidal geometry while retaining some of the stereochemical character of that coordination. For example, the axial bond angle between N3 and N5 is nearly the expected value of 180°. However, the “equatorial” angles are not uniform in values and deviate significantly from the ideal value of 120° (one of them being ca. 110°, and another one as large as 131°). The nitrito complex [Cu{N(CH2-py)3}(O–NO)]ClO4 (II) crystallizes in the monoclinic, space group I2/a (No. 15) with a=14.7787(4), b=9.1408(2), c=30.7316(5) Å, β=92.462(4)°, V=4147.67(7) Å3, Z=8; Dcalc=1.599 mg/m3. The same remarks concerning the geometry of (I) apply to that found in (II). This is very evident from the matchit diagram shown in Fig. 5, see text. The cyclic voltammetry characteristics of (II) and (III) were recorded and found to be very similar, especially in the values of the one-electron reduction and the two-electron oxidation potentials. The visible solution spectra, obtained in different solvents, for all three are consistent with an approximate TBP geometry and reveal the presence of linkage isomerization. The solid IR spectra for II confirm the aniso-bidentate nature of the O–N–O group in (II) and the N-bonded NCS− mode in (III).