Abstract :
Two crystalline phases, 1a, 1b, of [CuBr2(sp)] complex (sp ¼ (2)-sparteine) were obtained by direct synthesis. Crystal data: complex
1a, triclinic, P1, a ¼ 7:4715ð6Þ A ° , b ¼ 7:7082ð7Þ A ° , c ¼ 9:1435ð6Þ A ° , a ¼ 97:429ð6Þ8;b ¼ 112:808ð5Þ8;g ¼ 110:666ð6Þ8; complex 1b,
orthorhombic, P212121, a ¼ 11:0563ð7Þð6Þ A ° , b ¼ 11:9877ð9Þ A ° , c ¼ 12:8002ð9Þ A ° . The molecular locality of Cu(II) ion is
tetra-coordinated in each case and show close values of angle and bonds length for 1a, 1b. The UV-Vis and IR spectra of 1a and 1b
are very similar. 1H NMR spectra of 1a, 1b, are typical of Cu(II) paramagnetic complexes with broad lines in a range between 34 to
221 ppm. ESR spectra at 300 and 77 K of a polycrystalline sample for complex 1a show a broad signal with g ¼ 2:036: Two species
Cu(II) are developed by power saturation study. For 1b the ESR spectrum at 300 K is a singlet with composition Lorentzian 20%/Gaussian
80%. At 77 K the ESR singlet is still narrower with Lorentzian 90%/Gaussian 10%. The ratio areas is A77=A300 ¼ 5:22: All this features
indicate clearly a weak ferromagnetic Cu· · ·Cu exchange interaction. Standard magnetization measurements at low temperatures show that
cupric ion pairs exchange interact weakly, obtaining J1a ¼ l2:56l cm21 and J1b ¼ l1:93l cm21. The crystallographic data correlate quite
well with 1H NMR results such as: the line shapes, the relative areas and position of the signals, with the hydrogen atoms-spheres that
interact with the central copper ion.
q 2004 Elsevier B.V. All rights reserved.
