Low-Temperature Behavior of the Heat Capacity and Photoluminescence of the Binuclear Pivalate Complex [Eu2(Bаth)2(Piv)6]

The low-temperature behavior of the heat capacity and photoluminescence of the earlier structurally characterized binuclear pivalate complex [Eu₂(Bath)₂(Piv)₆] (monoclinic crystal system, I2/a) (I), where Bath = 4,7-diphenyl-1,10-phenanthroline, Piv = \({{{\text{(C}}{{{\text{H}}}_{{\text{3}}}}{\text{)}}}_{{\text{3}}}}{\text{CCO}}_{2}^{ - }\), is studied. The temperature dependence of the heat capacity in a temperature range of 5.96–302.88 K is measured by adiabatic calorimetry, and the thermodynamic functions \(C_{p}^{^\circ }\)(T), S°(T), Ф°(Т), and Н°(Т) – Н°(0) are calculated. The absence of low-temperature phase transitions in complex I is shown. In a temperature range of 98–295 K, complex I demonstrates a high temperature stability of the integral photoluminescence intensity of the ⁵D₀–⁷F_j (j = 0–6) transitions of the Eu³⁺ ion.