HIGH-SPIN MANGANESE(II) PHTHALOCYANINES - PREPARATION AND SPECTROSCOPICAL PROPERTIES OF ACIDOPHTHALOCYANINATOMANGANATE(II)

Acidophthalocyaninatomanaganese(III) is reduced by boranate, thioaceta te or hydrogensulfide to yield acidophthalocyaninatomanganate(II) ([Mn (X)Pc2-]-; X = Cl, Br, NCO, NCS) being isolated as tetra(n-butyl)ammon ium salt. In the cyclovoltammogram of [Mn(NCO)Pc2-]- the halv-wave pot ential for the redoxcouple Mn(II)/Mn(III) is at -0.13 V, that of the f irst ring reduction at -0.99 V. The magnetic moments are indicative of high-spin 6A1 ground states: mu(Mn) = 5.84 (NCO), 5.78 (Cl), 5.65 (Br ), 5.68 mu(B) (NCS). A Curie-like temperature dependence Of chi(Mn) is observed in the region 300 - 30 K. Below 30 K an increase in chi(Mn) occurs due to weak intermolecular ferromagnetic coupling. The ESR spec tra confirm the S = 5/2 ground state with a strong g = 6 resonance obs erved (A(Mn) = 80 G) as expected for an axially distorted ligand-field . Besides the typical pi - pi transitions of the Pc2-- ligand several weak bands are observed in the Uv-vis-n.i.r. spectra at ca. 7.5, 9.1, 14.0 and 19.0 kK that are assigned to trip-multiplet transitions. In resonance with the band at 19.0 kK the Mn-X stretching vibration (nu(M nX)) is resonance Raman enhanced: X = NCO: 319, Cl: 286, SCN: 238, Br: 202 cm-1. These vibrational frequencies are confirmed by the f.i.r. s pectra. In the case of the thiocyanato-complex probably both forms of bonding of the ambident NCS-ligand are present (nu(Mn-NCS): 274 cm-1). The frequencies of the vibrations of the inner (CN)8 ring are reduced by up to 20 cm-1 as compared with those of low spin Mn(II) phthalocya nines.