Dicopper(I) Complexes with Reduced States of 3,6-Bis(2‘-pyrimidyl)-1,2,4,5-tetrazine:  Crystal Structures and Spectroscopic Properties of the Free Ligand, a Radical Species, and a Complex of the 1,4-Dihydro Form

Abstract

The complexes [(mu-bmtz(*-))[Cu(PPh(3))(2)](2)](BF(4)) (1) and [(mu-H(2)bmtz)[Cu(PPh(3))(2)](2)](BF(4))(2) (2) (bmtz = 3,6-bis(2'-pyrimidyl)-1,2,4,5-tetrazine and H(2)bmtz = 1,4-dihydro-3,6-bis(2'-pyrimidyl)-1,2,4,5-tetrazine) were obtained as stable materials that could be crystallized for structure determination. 1.2 CH(2)Cl(2): C(84)H(70)BCl(4)Cu(2)F(4)N(8)P(4); monoclinic, C2/c; a = 26.215(7) A, b = 22.122(6) A, c = 18.114(5) A, beta = 133.51(1) degrees; Z = 4. 2.CH(2)Cl(2): C(83)H(70)B(2)Cl(2)Cu(2)F(8)N(8)P(4); triclinic, P1; a = 10.948(2) A, b = 12.067(2) A, c = 30.287(6) A, alpha = 93.82(3) degrees, beta = 94.46(3) degrees, gamma = 101.60(3) degrees; Z = 2. Bmtz itself was also structurally characterized (C(10)H(6)N(8); monoclinic, P2(1)/c; a = 3.8234(8) A, b = 10.147(2) A, c = 13.195(3) A, beta = 94.92(3) degrees; Z = 2). Whereas the radical complex ion contains a planar tetrazine ring in the center, the 1,4-dihydrotetrazine heterocycle in the corresponding complex of H(2)bmtz is considerably folded. Both systems exhibit slight twists between the tetrazine and the pyrimidine rings. The intra-tetrazine distances are characteristically affected by the electron transfer, as is also evident from a comparison with the new structure of free bmtz; the bonding to copper(I) changes accordingly. Spectroscopy including X- and W-band EPR of the radical species confirms that the electron addition is mainly to the tetrazine ring.

Luminescent homodinuclear copper(I) halide complexes based on the 3,5-bis{6-(2,2′-dipyridyl)}pyrazole ligand

“…The interplanar separations are less than 3.6 Å, which are below the upper limit of 3.8 Å for typical π-π interactions detected for most aromatic compounds [24], showing the existence of weak intramolecular π-π interactions between the pyrazolyl fragment and two phenyl rings above and beneath the pyrazolyl plane. Different from the reported mono-and binuclear copper(I) complexes containing both triphenylphosphine and diimine ligands [8][9][10][11][12][13][14][15][25][26][27], it is surprisingly noted that Cu-N distances (2.229(8) and 2.187(7) Å) for the inner pyridine rings of HL are notably longer than Cu-N distances (2.037(7) and 2.009(8) Å) of the peripheral pyridine rings, resulting likely from the steric interference between triphenylphosphines and the pyrazolyl fragment of adjacent HL.…”

“…These two reaction intermediates with the general formula (PPh 3 ) 2 Cu (μ-X) 2 Cu(PPh 3 ) (X = Br; I) are air-stable and easily soluble in dichloromethane, and they show similar solid-state emission profiles with identical peak maximum at 509 nm (excitation at 360 nm) at room temperature, assigned to the ligand PPh 3 [21]. In sharp contrast to the reported dicopper(I) complexes [8][9][10][11][12][13][14][15], it is surprising to note that the resulting complexes 1 and 2 are not only very air-stable in the solid state but also insoluble in common solvents such as dichloromethane, chloroform, acetonitrile, acetone, methanol, ethanol, ethyl acetate, and THF. Taking into account the above factors, a more simplified doublelayer diffusion method [22] was executed to grow the single crystals of Inorganic Chemistry Communications 13 (2010) 1057-1060 complexes 1 and 2, and actually the simple approach was subsequently confirmed to be extremely easy and efficient.…”

“…Many Cu(I) mixedligand complexes have been found to be air-stable and emissive in both solution and solid states, and their photoluminescence behavior varies with structural characteristics, identities of halides, and steric and electronic effects of coordinating ligands [6,7]. Recently, some homodinuclear copper(I) mixed-ligand complexes with the general formula [{Cu (PPh 3 ) 2 } 2 (μ-BL)] (BL =bridging bis-chelating ligand) have been found in the literature [8][9][10][11][12][13][14][15]. However, to the best of our knowledge, the luminescent binuclear copper(I) halide complexes [{Cu(PPh 3 )X} 2 (μ-BL)] (X = halide ligands) have not been reported hitherto.…”

Density Functional Study of Electron Paramagnetic Resonance Parameters and Spin Density Distributions of Dicopper(I) Complexes with Bridging Azo and Tetrazine Radical-Anion Ligands

“…Table 9 shows computed g-shift tensors for the free ligand radical anions. As one might expect for typical organic π-radicals, the anisotropies are much reduced compared with the complexes, with g 33 (the component perpendicular to the molecular plane) near g e and g 11 and g 22 about 2-7 ppt above g e , depending on the spin densities on nitrogen centers, which are responsible for the predominant spin-orbit contributions in the free radical anions. The much less pronounced dependence of the computed g-tensors on the exchange-correlation functional for the free ligands compared with the complexes (cf.…”

Synthesis and Reactivity Towards Cationic Group 11 Metal Centers of an Extended Silacalix-[3]-phosphinine Macrocycle

“…On the other hand, phosphorusϪcopper bond lengths compare with those recorded in other phosphinine [11] and tertiary phosphane Cu I complexes. [12] Another interesting feature is provided by the analysis of metric parameters within the phosphinine subunits. Apart from the opening of the internal PϪCϪP angle, which ranges from 105.3(1) in 4 to 108.8(1) in 8 as a result of the re-hybridization at phosphorus, bond lengths and angles are not dramatically modified.…”