Luminescent Properties of Phosphonate Ester-Supported Neodymium(III) Nitrate and Chloride Complexes.

This study examines the synthesis of two geminal bisphosphonate ester-supported Ln complexes [Ln()(NO)] (Ln = Nd (), La ()) and optical properties of the neodymium(III) complex. These results are compared to known mono-phosphonate ester-based Nd complexes [Nd(/)X] (X = NO, n = 1; Cl, n = 2) (-). The optical properties of Nd compounds are determined by micro-photoluminescence (µ-PL) spectroscopy which reveals three characteristic metal-centered emission bands in the NIR region related to transitions from F excited state. Additionally, two emission bands from F, H → I (J = 11/2, 13/2) transitions were observed. PL spectroscopy of equimolar complex solutions in dry dichloromethane (DCM) revealed remarkably higher emission intensity of the mono-phosphonate ester-based complexes in comparison to their bisphosphonate ester congener. The temperature-dependent PL measurements enable assignment of the emission lines of the F → I transition. Furthermore, low-temperature polarization-dependent measurements of the transitions from R and R Stark sublevel of F state to the I state for crystals of [Nd()(NO)] () are discussed.