Di- and Tetra-Nuclear Copper(II), Nickel(II), and Cobalt(II) Complexes of Four Bis-Tetradentate Triazole-Based Ligands: Synthesis, Structure, and Magnetic Properties

Abstract

Four bis-tetradentate N(4)-substituted-3,5-{bis[bis-N-(2-pyridinemethyl)]aminomethyl}-4H-1,2,4-triazole ligands, L(Tz1)-L(Tz4), differing only in the triazole N(4) substituent R (where R is amino, pyrrolyl, phenyl, or 4-tertbutylphenyl, respectively) have been synthesized, characterized, and reacted with M(II)(BF(4))(2)·6H(2)O (M(II) = Cu, Ni or Co) and Co(SCN)(2). Experiments using all 16 possible combinations of metal salt and L(TzR) were carried out: 14 pure complexes were obtained, 11 of which are dinuclear, while the other three are tetranuclear. The dinuclear complexes include two copper(II) complexes, [Cu(II)(2)(L(Tz2))(H(2)O)(4)](BF(4))(4) (2), [Cu(II)(2)(L(Tz4))(BF(4))(2)](BF(4))(2) (4); two nickel(II) complexes, [Ni(II)(2)(L(Tz1))(H(2)O)(3)(CH(3)CN)](BF(4))(4)·0.5(CH(3)CN) (5) and [Ni(II)(2)(L(Tz4))(H(2)O)(4)](BF(4))(4)·H(2)O (8); and seven cobalt(II) complexes, [Co(II)(2)(L(Tz1))(μ-BF(4))](BF(4))(3)·H(2)O (9), [Co(II)(2)(L(Tz2))(μ-BF(4))](BF(4))(3)·2H(2)O (10), [Co(II)(2)(L(Tz3))(H(2)O)(2)](BF(4))(4) (11), [Co(II)(2)(L(Tz4))(μ-BF(4))](BF(4))(3)·3H(2)O (12), [Co(II)(2)(L(Tz1))(SCN)(4)]·3H(2)O (13), [Co(II)(2)(L(Tz2))(SCN)(4)]·2H(2)O (14), and [Co(II)(2)(L(Tz3))(SCN)(4)]·H(2)O (15). The tetranuclear complexes are [Cu(II)(4)(L(Tz1))(2)(H(2)O)(2)(BF(4))(2)](BF(4))(6) (1), [Cu(II)(4)(L(Tz3))(2)(H(2)O)(2)(μ-F)(2)](BF(4))(6)·0.5H(2)O (3), and [Ni(II)(4)(L(Tz3))(2)(H(2)O)(4)(μ-F(2))](BF(4))(6)·6.5H(2)O (7). Single crystal X-ray structure determinations revealed different solvent content from that found by microanalysis of the bulk sample after drying under a vacuum and confirmed that 5', 8', 9', 11', 12', and 15' are dinuclear while 1' and 7' are tetranuclear. As expected, magnetic measurements showed that weak antiferromagnetic intracomplex interactions are present in 1, 2, 4, 7, and 8, stabilizing a singlet spin ground state. All seven of the dinuclear cobalt(II) complexes, 9-15, have similar magnetic behavior and remain in the [HS-HS] state between 300 and 1.8 K.

A Smorgasbord of 17 Cobalt Complexes Active for Photocatalytic Hydrogen Evolution

“…These purely N-donor Trz ligands vary in the triazole N 4 substituent, and in the length of one of the two pyridine arms on either side of the triazole, giving variation in the chelate ring sizes formed by the tetradentate pockets. The dinuclearc obalt complexes [Co II [23] are each derived from ad ifferent polypyridyl Trz ligand,s op resent an interesting series in which to probe the Chem. Eur.J.…”

“…PSPhT, [27] PS Me PhT, [27] PSiBuT, [27] Pydz Et , [28] Pydz Et/Et , [29] and Pym Et/Me [30] were prepared as reported previously.C omplexes [Co II 2 ( tBuPh Trz Me/Me )(m-BF 4 )](BF 4 ) 3 , [23] [Co II 2 ( pyrr Trz Me/Me )(H 2 O) 2 ](BF 4 ) 4 , [23] [Co II 2 (Pydz Et )(m-Cl)Cl 2 ]Cl, [Co II 2 (Pydz Et/Et )(m-OH)](BF 4 ) 3 · 1 = 2 H 2 O, [29] [Co II (M Et )]BF 4 , [26a] [Co II (M Pr )]BF 4 , [26b] [Co( Br M Et )]BF 4 , [31] [ [24a] [Co III (dmgH) 2 (py)Cl], [32] [Ru-(bpy) 3 ](PF 6 ) 2 , [33] and [Ru(bpy) 3 ]Cl 2 [33] were prepared as previously described.…”

N-(5-Amino-1H-1,2,4-triazol-3-yl)pyridine-2-carboxamide

“…For background to triazole derivatives, see: Aromí et al (2011); Olguín et al (2012). For related triazole structures, see: Allouch et al (2008); Ouakkaf et al (2011).…”

Carbon Dioxide Fixation and Sulfate Sequestration by a Supramolecular Trigonal Bipyramid

“…Thel igands forming the edges of the trigonal bipyramid exhibit extensive face-to-face aromatic stacking (Figure 2b), defining two separate cavities that are separated by the equatorial ring of Zn II centers.ABF 4 À ion is bound in each binding pocket, stabilized by attractive electrostatic forces and CH···F hydrogen-bonding interactions with the protons lining the interior of the binding pocket. At hird BF 4 À ion is bound at the equator of 4 and acts as at ris(monodentate) ligand, [27] bridging the three equatorial Zn II centers with three of its fluorine atoms.T wo of these Zn II ions are each coordinated to an additional hydroxide ion;the equatorial belt thus consists of two six-coordinate Zn II centers and one five-coordinate Zn II ion. At hird BF 4 À ion is bound at the equator of 4 and acts as at ris(monodentate) ligand, [27] bridging the three equatorial Zn II centers with three of its fluorine atoms.T wo of these Zn II ions are each coordinated to an additional hydroxide ion;the equatorial belt thus consists of two six-coordinate Zn II centers and one five-coordinate Zn II ion.…”

“…An analysis of the 19 FNMR spectrum revealed that the bound BF 4 À ions were in slow exchange on the NMR timescale in solution ( Figure S15), with correlations to inward-facing host protons detected in the 19 F-1 HHOESY spectrum ( Figure S16). At hird BF 4 À ion is bound at the equator of 4 and acts as at ris(monodentate) ligand, [27] bridging the three equatorial Zn II centers with three of its fluorine atoms.T wo of these Zn II ions are each coordinated to an additional hydroxide ion;the equatorial belt thus consists of two six-coordinate Zn II centers and one five-coordinate Zn II ion. Several combinations of water, hydroxide,a nd acetonitrile adducts were detected in the HRMS spectrum after dissolving the crystals of 4 in acetonitrile ( Figure S19), suggesting dynamic exchange of these weakly bound ligands at the equatorial positions in solution.…”