Band gap engineering in pyridyl-functionalized two-dimensional (2D) CuSCN coordination polymers

31 January 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Copper(I) thiocyanate (CuSCN) has emerged as an excellent hole-transporting semiconductor with applications spanning across electronic and optoelectronic fields. The coordination chemistry of CuSCN allows for extensive structural versatility via ligand modification. In this work, we have developed a synthetic method that reliably produces phase pure [Cu(SCN)(3-XPy)]n complexes (Py = pyridyl; X = OMe, H, Br, and Cl) in a 1:1:1 ratio to yield two-dimensional (2D) structures with a Cu-SCN network. The single crystal structure of [Cu(SCN)(3-OMePy)]n is also reported herein. Complexes with X = OMe and H show similar structures, in which the 2D layers are analogous to the buckled 2D sheets of silicene or blue phosphorene. On the other hand, for complexes with X = Br and Cl, their rippled 2D structures resemble the puckered 2D sheets found in black phosphorene. The variation of the electron-withdrawing ability of the substituent group is found to systematically shift the electronic energy levels and band gaps of the complexes, allowing the 2D CuSCN-based materials to display optical absorptions and emissions in the visible range. In addition, first-principles calculations reveal that the drastic change in the electronic levels is a result of the emergence of the Py ligand electronic states below the SCN states. This work demonstrates that the structural, electronic, and optical properties of 2D Cu-SCN networks can be systematically tailored through ligand modification.


Copper(I) thiocyanate
coordination polymers
2D materials
ligand modification

Supplementary materials

Supplementary information
Supplementary figures: ATR-IR, PXRD, structural comparison, TGA, PYS, electronic band structures, isosurface charge densities, density of states. Supplementary tables: crystallographic data and structural refinement parameters, comparison of lattice parameters and band gaps from experimental and computational results.


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