Manganese(II) complexes of hexaazatrinaphthylene and hexaazatrianthracene: synthesis, structure and properties

Complexes of high-spin (S = 5/2) manganese(II) with hexaazatrinaphthylene (HATNA) and hexaazatrianthracene (HATA) dianions and radical trianions have been obtained in a crystalline form. Neutral HATNA is coordinated with only one Mn-II(dedtc)(2) fragment (dedtc: diethyldithiocarbamate) in [{Mn-II(dedtc)(2)}(HATNA)](0) (1) with long Mn-II-N(HATNA) bonds of 2.390(5) & Aring;. The HATNA dianions are coordinated with three Mn-II(dedtc)(2) or Mn-II(acac)(2) units in {(K+)(crypt)}(2)[{Mn-II(dedtc)(2)}](3){(HATNA)}(2-)2C(6)H(4)Cl(2) (2) and {(K+)(crypt)}(2)[{Mn-II(acac)(2)}(3){(HATNA)}](2-)2C(6)H(4)Cl(2)C6H14 (3) (crypt is cryptand[2.2.2]) with shorter Mn-II-N(HATNA) bonds of 2.252(3) and 2.287(4) & Aring; length, respectively. The Mn-II-N(HATA or HATNA) bonds are shortened to 2.160(4) and 2.110(4) & Aring; in dianionic (CV+)(2)[((MnCl2)-Cl-II)](3){(HATA)}(2-)4C(6)H(4)Cl(2) (4) and trianionic {(K+)(crypt)}(3) {((MnI2)-I-II)(3)(HATNA)}(3-)5C(6)H(4)Cl(2) (5) complexes, respectively (CV+ is a crystal violet cation). It is shown that the Mn-II-N bonds in 1-5 are longer in comparison with the Fe-II-N and especially Co-II-N bonds. Weak antiferromagnetic Mn-II-Mn-II coupling with J values of -1.98 and -2.70 cm(-1) is observed for diamagnetic ligands in 2 and 4. The paramagnetic HATNA(center dot)(3-) ligand (S = 1/2) leads to the additional antiferromagnetic Mn-II-HATNA(center dot)(3-) coupling with a J value of -6.6 cm(-1) in 5, which coexists with weaker Mn-II-Mn-II coupling with a J value of -0.6 cm(-1). As a result, the chi T-M value in 5 only weakly depends on temperature. Thus, the Mn-II-HATNA(center dot)(3-) and Mn-II-Mn-II couplings are noticeably smaller than those in previously studied Co-II and Fe-II assemblies. Zero-field splitting parameter D is rather high for manganese(II) ions in 2, 4 and 5 being -3.1 to -4.6 cm(-1). Weaker exchange coupling allows the observation of both EPR signals from Mn-II and the paramagnetic ligand. An isotropic EPR signal from Mn-II with a g-factor of 2.03-2.04 is observed in 2 in the whole studied temperature range. An isotropic EPR signal is also observed in 4 with g = 2.0346 at 295 K. This signal shifts to a lower g-factor at 100 K, whereas low-field components appear only at 4.5 K. The contribution from HATNA(center dot)(3-) in 5 probably decreases the g-factor to 2.0017 at 295 K. Zero-field splitting of the EPR signal for Mn-II is manifested at 4.2 K.