Family of Robust and Strongly Luminescent CuI-Based Hybrid Networks Made of Ionic and Dative Bonds

Abstract

The CuI-derived inorganic−organic hybrid compounds are considered as promising phosphors for the lighting industry. Herein, exploiting N-monoalkylated hexaminium salts, [R-HMTA]X (R = Me, Et, Pr, and propargyl; X = Cl and I), as multibridging ligands, we have designed and synthesized a unique class of one-dimensional and two-dimensional hybrid CuImaterials. The reactions of these salts with CuI give rise to Allin-One (AIO) type compounds combining ionic and dative bonds between inorganic and organic components. The latter is formed by structurally unique inorganic [Cu x I y ] (y−x)− clusters, chains, or sheets interconnected through [R-HMTA] + cations via multiple Cu−N bonds. The so-designed compounds at ambient temperature exhibit tunable luminescence spanning from deep blue to red color (λ em = 430−625 nm) with microsecond lifetimes and the quantum efficiency of up to 78%. Remarkably, the AIO materials feature nontrivial excitation-(ED) and temperature-dependent (TD) luminescence, allowing their emission color to be finely adjusted from deep blue to red through changing the excitation wavelength and/or temperature. Based on the TD emission spectroscopy and theoretical calculations, a possible mechanism of the luminescence has been proposed. The very interesting luminescence characteristics coupled with good thermal and photostability render these AIO hybrid materials possible candidates for applications in energy-efficient lighting devices.

Coordinated Anionic Inorganic Module—An Efficient Approach Towards Highly Efficient Blue‐Emitting Copper Halide Ionic Hybrid Structures

“…Also, the solution processability has been much enhanced due to the ionic bonding in these structures. However, those structures are typically considered as “ligand‐free” structures, as there is no coordinate bond between the ligands and the Cu atoms [10] . Such structural change compared to the original ligand‐coordinated structures leads to the absence of organic‐ligand‐related excited states upon excitation, including metal‐to‐ligand charge transfer (MLCT), halide‐to‐ligand charge transfer (XLCT) etc., resulting in luminescence quenching [5d, 11] .…”

All-in-one: a new approach toward robust and solution-processable copper halide hybrid semiconductors by integrating covalent, coordinate and ionic bonds in their structures

“…5c ). 32 This was confirmed by the Density Function Theory (DFT) calculations. The valence band maximum (VBM) of the copper iodide AIO compounds is primarily composed of the inorganic atomic states, specifically Cu 3d and I 5p orbitals, and the conduction band minimum (CBM) is populated either by organic components ( i.e.…”

“… 1,25,29–31,35,39,60,68 Interestingly, when the Cu⋯Cu distance falls to the borderline, both pathways, namely CC and (M + X)LCT, can occur simultaneously and show responsive dual emissions as a function of excitation energy and/or temperature. 32 …”

“…Electronic state calculations on the aliphatic ligand based AIO extended networks (with an average Cu⋯Cu distance of ∼2.80 Å) show that both inorganic and organic motifs contribute to the CBM, suggesting both CC and (M + X)LCT emission pathways are possible. 32 However, depending on the Cu⋯Cu distances and structural rigidity, one or both processes may play a dominating role. Structures with relatively short average Cu⋯Cu distances and high flexibility exhibit comparable emissions from both pathways.…”

“…temperature or excitation wavelength), resulting in responsive dual emitters towards temperature and excitation energy. 32 For example, the emission color of 1D-Cu 4 I 6 ( Pr-hmta ) 2 , with average Cu⋯Cu distance of 2.80 Å and relatively flexible structures, can be smoothly adjusted from cyan to orange-red by changing excitation wavelength from 260 to 380 nm or lowering the temperature from 300 K to 77 K. On the other hand, AIO compound 2D-Cu 6 I 8 ( Pr-hmta ) 2 ( MeCN ) 2 constructed with same ligand but have longer average Cu⋯Cu distance (3.06 Å) and higher structural rigidity only displays one emission band within 77–300 K window, which may be attributed to the destabilized 3 CC state caused by longer average Cu⋯Cu distances and higher rigidity.…”