Preparation, Structure and Spectroscopic Properties of NH4[Ln(S2CNH2)4] ⋅ H2O (Ln=La, Eu)

Abstract The title compounds were prepared under mild ambient conditions by a facile co‐precipitation route. NH 4 [Eu(S 2 CNH 2 ) 4 ] ⋅ H 2 O ( a ) and NH 4 [La(S 2 CNH 2 ) 4 ] ⋅ H 2 O ( b ) crystallize isotypically in the monoclinic space group P 2 1 / c with a =8.4461(3), b =13.6367(3), c =16.2945(5) Å, β =103.759(2)° (for ( a )), and a =8.50484(9), b =13.84476(16), c =16.20816(17) Å, β =103.7644(11)° for ( b ), respectively. The spectroscopic data reveal the presence of a l igand‐to‐ m etal c harge t ransfer (LMCT) process of low energy in a and in the solid solutions NH 4 [La 1−x Eu x (S 2 CNH 2 ) 4 ] ⋅ H 2 O (x=0.016 and 0.05). Despite of the consequent efficient luminescent quenching, it was possible to recorded excitation and emission spectra at room temperature. These spectra are characterized by narrow bands due to intraconfigurational‐4f transitions of the Eu 3+ ion. However, broad bands associated to the LMCT state were also observed, mainly for the solid solutions NH 4 [La 1−x Eu x (S 2 CNH 2 ) 4 ] ⋅ H 2 O (x=0.016 and 0.05). Consequently, an intramolecular energy transfer mechanism is proposed, taking into account the role of the LMCT on the spectroscopic properties of dithiocarbamate complexes.