Structural Features, Emission Analysis, and Covalency Comparison of Neodymium Acylpyrazolone Complexes using Oscillator Strengths, Covalency and Judd‐Ofelt Parameters**

Abstract

Three distorted square antiprismatic eight coordinated neodymium acylpyrazolone complexes were synthesized having the compositions [Nd(L1)3(H2O)(EtOH)] (NdL1), [Nd(L2)3(H2O)(EtOH)] (NdL2), and [Nd(L3)3(H2O)(EtOH)] (NdL3). The structure of all three complexes was examined using ESI‐mass, FT‐IR, and thermogravimetric methods. According to the single crystal analysis of NdL1, the complex was found eight‐coordinated (NdO8) with a distorted square antiprismatic geometry. A powder XRD pattern confirmed a similar structural arrangement of the other two complexes. In electronic absorption spectra, the transition 4G5/2←4I9/2, which is close to the centre of the visible spectrum (~17,500 cm−1), exhibits hypersensitivity, which stands out in stark contrast to the behaviour of many other typically weak and reliably unchanging, typical 4f–4f transitions. Through a comparative analysis of calculated oscillator strength, Judd‐Ofelt parameters, root mean square deviation, radiative lifetime and covalency parameters in various solvents, hypersensitivity, symmetry characteristics, and covalency have been thoroughly investigated. The promotion of 4f–4f electric‐dipole intensity has been found to be particularly successful with ethanol, pyridine, DMF, and DMSO. Utilizing Judd‐Ofelt Ω4 values and Hirshfeld analysis, long‐range secondary π⋅⋅⋅π stacking or H‐bonding interactions were investigated. The intensity of emission spectra, quantum yield, stokes shift, and antenna effect energy diagram was examined using solid‐state emission spectra.