Copper(I)‐Assisted Formation of an “Organic” Sandwich Structure: Structural Prerequisites for Luminescence of the Dinuclear Complexes [(μ‐Bipyrimidine){Cu(PR₃)₂}₂]X₂

Abstract

Weak inter-or intramolecular interactions, especially when combined and integrated into appropriate molecular "architecture", can lead to the formation of supramolecular structures with specific functionality."] Here we report a system that, owing to such interactions in the solid, shows strong luminescence from a metal-to-ligand charge-transfer (MLCT) excited state.Compounds 1-3, which belong to the class of homodinuclear complexes containing the bridging ligand 2,T-bipyriml a

Synthesis and characterization of mono- and dinuclear copper(I) complexes with 3-(2-pyrimidinyl)-1,2,4-triazine

“…The Cu-N bond distances (2.099(4) and 2.120(4) Å ) are slightly longer than those of the reported compound [CuI(PPh 3 )(bipy)] [28,29], while the bond lengths of Cu-P (2.1971(15) Å ) and Cu-I (2.5955(8) Å ) are comparable to those observed in related copper(I) complexes [28][29][30]. The N-Cu-N bond angle is 77.72(17)°, somewhat smaller than those reported in the literature [23,24,[28][29][30]. It is notable that the pmtz ligands from two adjacent molecules are basically parallel and show a favorable pairwise p-p stacking (see Fig.…”

“…The blue-shift can be rationalized in terms of the lowering of the HOMO energy upon replacement of the iodide of 1 with a p-acceptor ligand PPh 3 , thus leading to an increase of the HOMO-LUMO energy gap. Compared with the absorption spectrum (k max = 438 nm) of [{Cu(PPh 3 ) 2 } 2 (l-bpym)](ClO 4 ) 2 [23], the lower-energy absorption peak (k max = 407 nm) of complex 2 has a blue-shift of around 31 nm due to introduction of one additional nitrogen donor relative to 2,2 0 -bipyrimidine, resulting in an increase of the HOMO-LUMO energy gap. Complexes 1 and 2 featuring the pmtz ligand are found to be non-emissive, while an analogous compound [{Cu(PPh 3 ) 2 } 2 (l-bpym)](ClO 4 ) 2 has been reported to be photoluminescent in both the solid state and in chloroform solution [23].…”

“…For complex 1, there are several absorption bands ranging from 225 to 350 nm with intense molar extinction coefficients e [ 10 4 M -1 cm -1 , and a relatively weaker absorption (e \ 6.5 9 10 3 M -1 cm -1 ) at k max = 442 nm. With reference to previous work on Cu(I) complexes possessing the N,N-donor ligands [23,24,[32][33][34][35], the high-energy strong absorption bands at the range 225-350 nm are most likely originated from the ligand-centered 1 pp* transitions, while the lowerenergy weak absorption peak at 442 nm can be identified as a metal-to-ligand charge transfer (MLCT) transition from the d p orbital of the (3d 10 ) Cu center to the unoccupied p* orbital of the pmtz ligand, probably mixed with some halide-to-ligand charge transfer (XLCT) I ? pmtz transition.…”

“…Many bpymbased homo-and heterobimetallic complexes including derivatives of Ru [18], Os [19], Pt [20], Re [21], and Cu [22] have been reported. Of these, the Cu(I)-bpym species are found to be emissive in both solution and solid state at ambient temperature [23,24]. Similar to bpym, 3-(2-pyrimidinyl)-1,2,4-triazine (pmtz) is also a bis-bidentate bridging ligand but asymmetrical due to introduction of an additional nitrogen atom.…”

Switching‐on: The Copper Age

“…Only a few examples of binuclear systems are in the diimine complex literature: these use bipyrimidine [65], 2,5-bis(2-pyridyl)pyrazine ligands [56], or others [57]. A downside encountered is that the potential rigidity is reduced, for example, in a transoid disposition.…”