Coordination complexes of reduced organic dye isoviolanthrone with transition metals and lanthanides [Mn(II), Dy(III), Gd(III), Nd(III)]

Abstract

The reduction of a vat dye isoviolanthrone to the dianion state in the presence of metal-containing compounds yields binuclear coordination complexes. Two manganese(II) acetylacetonate units coordinate to isoviolanthrone2- 2- (L) in {(K+)cryptand}2{[MnII(acac)2]2 & sdot;L}2- + )cryptand} 2 {[Mn II (acac) 2 ] 2 & sdot; L} 2- (1) 1 ) with an average Mn-O bond length of 2.022(2) & Aring;. Dysprosium(III)- or gadolinium(III)-2,2,6,6-tetramethyl-3,5-heptanedionate (TMHD) units form {(K+)crypt- + )crypt- and}2{[MIII(TMHD)3]2 & sdot;L}2- 2 {[M III (TMHD) 3 ] 2 & sdot; L} 2- (M = Dy III for 2 and Gd III for 3 ) with the length of the M-O bonds of 2.193(3) and 2.254(4) & Aring;, respectively. Tris(cyclopentadienyl)neodymium(III) forms {(Cs+)crypt- + )crypt- and}2{[Cp3NdIII]2 & sdot;L}2-& sdot;C6H4Cl2 2 {[Cp 3 Nd III ] 2 & sdot; L} 2- & sdot; C 6 H 4 Cl 2 (4) 4 ) with the Nd-O bonds of 2.264(2) and 2.308(2) & Aring; length. The formation of isoviolanthrone2- 2- is supported by their optical spectra, disappearance of the bands of the C--O -- O vibrations in the IR-spectra as well as elongation of the C--O - - O bonds in 1 - 4 . High-spin (S S = 5/2) MnII II atoms in 1 have exchange interaction of J =- 0.122 cm-- 1 at g = 1.98. Lanthanides have weaker coupling through isoviolanthrone2- 2- in 2 and 3 with J =- 0.029 and D =- 0.004 cm-- 1 for Dy III and J = 0.0019 cm-- 1 for GdIII. III . Complex 4 with two Cp3NdIII 3 Nd III species demonstrates the chi M T value of 2.33 emu & sdot;K/mol & sdot; K/mol at 300 K, and this value is lower than the theoretically calculated value of 3.39 emu & sdot;K/mol. & sdot; K/mol. The decrease of chi M T is observed in the whole 300-1.9 K range providing negative Weiss temperatures of -32 K. That is explained by magnetic behavior of Cp3NdIII 3 Nd III similar to pristine Cp3NdIII. 3 Nd III . Complexes comprising MnII, II , GdIII, III , and Nd III show electron paramagnetic resonance (EPR) signals. Zero-field splitting (ZFS) is observed from MnII II and Gd III allowing the estimation of zero-field splitting parameter D as- 0.047 and E close to 0 cm-1 for 1 and- 0.033 and- 0.020 cm-1 for 3 . Complex 4 with Nd III manifests an asymmetric two-component EPR signal without ZFS. Weak antiferromagnetic couplings are explained by diamagnetism of isoviolanthrone2- 2- and rather long distances between the metal centers of 15.47-16.25 & Aring;. This study shows that the dianions of organic dyes are promising bidentate ligands for preparation of coordination complexes with d- and f-block metal ions.