Organic ligands containing conjugated C=N bonds can significantly enhance photophysical behavior [1]. While Ag(I) coordination polymers exhibit intriguing photophysical properties [2], Ag(I) is more reactive and less stable than Cd(II), motivating the exploration of Cd(II)-based systems as viable alternatives. In this work, we report the synthesis, photochemical, and photoluminescent properties of a new Cd(II) complex, [CdL₂I₂H₂O], L = ethyl-5-amino-1-methyl-1H-pyrazole-4-carboxylate.

The obtained compound was characterized by ATR-FTIR, molar conductivity in DMF, and X-ray diffraction. Room temperature fluorescence of the samples was measured using a 355 nm UV solid-state pulsed laser.

White crystals of the complex [CdL₂I₂H₂O] were obtained by reacting CdI₂ with L in methanol and in its mixture with other solvents as MeCN, Me₂CO, and H₂O. In the obtained complex, L coordinates through the unsubstituted nitrogen atom of the pyrazole ring. The asymmetric unit of this mononuclear complex comprises one Cd(II), two N-coordinated pyrazole ligands, two iodido ligands, and one coordinated water molecule. The Cd(II) center adopts a distorted trigonal-bipyramidal geometry.

Complex shows strong near-UV to blue fluorescence. The compound emits at 393 nm (powder/pellet) with FWHM 72/80 nm; intensity rises from 44,600 to 151,687 a.u.

A novel mononuclear Cd(II) complex pyrazole derivative ligand was synthesized and characterized. With its simple and accessible synthesis, [CdL₂I₂(H₂O)] represents a promising candidate for advancing existing Cd(II)-based luminophores and exploring structure–property relationships in photoluminescent materials.

[1] Ristić, P.; Sreekala, C. O.; Kulkarni, N. V.; Senthurpandi, D.; Mathew, J. J. Mol. Struct. 2022, 1266, 133512. https://doi.org/10.1016/j.molstruc.2022.133512

[2] Ristić, P.; Filipović, N.; Blagojević, V. A.; Ćirković, J.; Barta Holló, B.; Đokić, V. R.; Donnard, M.; Gulea, M.; Marjanović, I.; Klisurić, O. R.; Todorović, T. R. CrystEngComm 2021, 23, 4799–4815. https://doi.org/10.1039/d1ce00394a