Partial in Situ Reduction of Copper(II) Resulting in One-Pot Formation of 2D Neutral and 3D Cationic Copper(I) Iodide–Pyrazine Coordination Polymers: Structure and Emissive Properties

Abstract

On the way to copper(I) iodide coordination polymers with specific luminescent properties, the in situ reduction of Cu(II) in the presence of KI and bidentate N-heteroatomic ligand, either pyrazine (pyz) or 4,4'-bipyridine (bpy), resulted in one two-dimensional and two three-dimensional new coordination networks. Starting from Cu(NO)·3HO in the presence of pyz, successive precipitation of known yellow [(CuI)(pyz)], new orange [CuI(pyz)], and new dark blue {[Cu(pyz)]·I} polymeric solids was observed. Starting from the same salt in the presence of bpy resulted in the successive precipitation of known yellow [(CuI)(bpy)] and new brown {[Cu(NO)(bpy)]·I·(dmf·HO)} coordination polymers. By using either Cu(CHCOO)·HO or Cu(BF) as starting materials, both known forms, yellow [(CuI)(bpy)] and orange [CuI(bpy)], precipitated successively. The new solids were characterized by IR spectroscopy and X-ray analysis. [CuI(pyz)] represents the missing member in the row of two-dimensional coordination networks with general formula [CuX(pyz)] (X = Cl, Br, I). Its steady state and time-resolved characterization together with DFT and TDDFT calculations revealed that the emission at room temperature is mainly delayed fluorescence originating from mixed singlet metal-to-ligand charge transfer and halide-to-ligand charge transfer states, while that at 77 K is phosphorescence, associated with the small singlet-triplet energy differences (ΔE = 70 meV).

Tuning the architectures and luminescence properties of Cu(i) compounds of phenyl and carboranyl pyrazoles: the impact of 2D versus 3D aromatic moieties in the ligand backbone

“…104 Note that there are only two cases of double emission in single-stranded Cu(I) polymers, both reported by Cariati. 3 Although similar results have been reported for double-stranded or grid-like Cu(I) polymers, 105,106 direct extrapolation should be avoided, as the latter can possess 3 CC based-emission 104,107 and they show completely different structures. The remarkable Stokes shift for polymer 1 is striking in comparison with the other three compounds (Table 2).…”

Mechanochemistry, an Easy Technique to Boost the Synthesis of CuI Pyrazine Coordination Polymers

“…Infinite double chains based on copper halides or pseudohalides have been investigated for their luminescence ,− and conductivity properties. ,− Several papers describe the structures and behavior of CuX pyrazine compounds, ,,− and recently the missing structure of the [CuI­(pyz)] n (pyz = pyrazine) has been published . With the awareness that the copper iodide reacts easily via mechanochemistry, we investigated the possibility to obtain and transform the CuI pyrazine compounds upon mechanical and thermal treatments.…”

Out with Acetonitrile: Water-assisted Accelerated-Aging Synthesis of CuI-Pyrazine Hybrid Materials

“…[51][52][53] CuI and pyrazine form three hybrid materials with extended structures (Figure 1), [(CuI)2(pyrazine)] (Yellow), which is constructed by extended (CuI)∞ staircase chains linked by the coordinating organic ligands, pyrazine, and packed in a zig-zag fashion; [(CuI)2(pyrazine)2] (Orange), which is constructed by (CuI)2 rhombus-shaped dimers that are connected by the ligands to form 2-D sheets, and [(CuI)(pyrazine)] (Red), which is constructed by 1-D CuI chains linked by the ligands to form 2-D sheets. Both Yellow and Red have been synthesized in solution 54,55 , as well as hydro/solvothermally 29,56 . Orange was synthesized using mechanochemical synthesis or by heating dry CuI and pyrazine at appropriate molar ratio.…”