Synthesis, crystal structure, and theoretical investigation of a half-sandwich iridium(III) complex bearing a pyrene-substituted BIAN ligand

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Abstract
A half-sandwich iridium(III) complex, [(η⁵-Cp*)Ir(Py-BIAN)Cl]PF₆, bearing a pyrene-substituted α-diimine ligand (Py-BIAN), has been synthesized and fully characterized. Single-crystal X-ray diffraction reveals a three-legged piano-stool geometry with κ²N,N′-chelating Py-BIAN and a terminal chloride. DFT benchmarking at six levels identifies CAM-B3LYP/def2-SVP/def2-TZVP as the best-performing method, which was then used to investigate the frontier molecular orbitals, ESP, UV-vis and FT-IR spectra, and excited-state energy levels. To understand how the pyrene-extended aromatic surface controls the solid-state organization, the intermolecular interactions were analyzed by a combination of IGMH, energy decomposition, and Hirshfeld surface methods. IGMH and Hirshfeld surface analyses reveal four C–H···X (X = Cl, F) hydrogen bonds and three π–π stacking interactions, with an interaction energy of −10.34 kcal mol⁻¹ between the two closest cationic complexes. Energy decomposition analysis shows that Complex···PF₆⁻ ion pairs are dominated by the Coulombic term (−303.50 to −181.56 kJ mol⁻¹), whereas Complex···Complex pairs are net repulsive (+26.51 to +48.25 kJ mol⁻¹) with a significant dispersion contribution (up to −107.78 kJ mol⁻¹). This work provides the first example of a pyrene-substituted BIAN–iridium(III) complex and a combined experimental and theoretical basis for understanding how the pyrene-extended BIAN environment controls its structure, electronic structure, and packing.

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