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. 2025 Oct 13;10(41):49074-49086.
doi: 10.1021/acsomega.5c07896. eCollection 2025 Oct 21.

Properties and Perspectives of Rb2Co(SO4)2(H2O)6 Tutton Crystal: A Combined Experimental-Theoretical Analysis

João G de Oliveira Neto  1 , Letícia F Gomes  1 , Francisco W S de Sousa Junior  1 , Djany S Silva  1 , Kamila R Abreu  1 , Luiz F L da Silva  2 , Luzeli M da Silva  1 , Pedro de F Façanha Filho  1 , Eliana B Souto  3 , Adenilson O Dos Santos  1 , Rossano Lang  4
Affiliations

Properties and Perspectives of Rb2Co(SO4)2(H2O)6 Tutton Crystal: A Combined Experimental-Theoretical Analysis

João G de Oliveira Neto et al. ACS Omega. .

Abstract

This paper presents a comprehensive investigation of a Tutton crystal, rubidium cobalt sulfate hexahydrate Rb2Co-(SO4)2(H2O)6, detailing its synthesis and characterizing its structural (PXRD), vibrational (FT-IR and Raman), thermal (TG and DSC), and optical (UV-vis-NIR) properties. Complementary, calculations using density functional theory (DFT) were implemented to estimate electronic band structure and assign optical phonon modes identified through FT-IR and Raman spectra. The material was prepared by the slow solvent evaporation method and crystallized, having P21/a-space group in the monoclinic system (unit cell parameters a = 9.204(9) Å, b = 12.467(2) Å, c = 6.246(3) Å, β = 106.02(5)°, and V = 688.93(4) Å3). Hirshfeld surface analysis and void calculations revealed a densely packed structure stabilized by strong O···H/H···O hydrogen bonds, followed by O···Co/Co···O contacts, with a void volume of only 1.4%. Thermograms show a full dehydration at ≈ 384 K (ΔH = 301.15 kJ/mol). While electronic band structure indicates an electronic bandgap of 3.00 eV, dominated by Co2+ d-orbital contributions, the optical measurements display an optical bandgap of ≈ 4.13 eV, attributed to ligand-to-metal charge transfer bands involving electron donation from the nonbonding orbitals of H2O to the Co2+ orbitals. The optical absorbance (200-300 nm) transmittance (300-420 nm/580-1100 nm) windows underscore the potential of Rb2Co-(SO4)2(H2O)6 crystal.

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Figures

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1. Experimental Procedure Used in the Synthesis of RbCoSOH Crystals
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(a) Experimental PXRD pattern refined by the Rietveld method for the powdered RbCoSOH crystals. Inset: Image of an RbCoSOH single crystal grown by slow solvent evaporation. (b) Polyhedral representation of the primitive unit cell for the RbCoSOH Tutton salt.
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(a) Rietveld method-refined primitive unit cell of RbCoSOH Tutton salt. 3D Hirshfeld surfaces mapped with different molecular interaction properties: (b) d norm, (c) d i, (d) d e, (e) shape index, and (f) curvedness.
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2D fingerprint plots (full and deconvoluted) generated from the refined unit cell of RbCoSOH Tutton salt.
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Crystal voids within the RbCoSOH primitive unit cell are visualized through isosurfaces along the c–a plane.
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Band structure plots as a function of energy for: (a) spin-up and (b) spin-down states of the RbCoSOH crystal calculated via DFT. (c) PDOS computations by orbital contributions (s, p, and d). The Fermi level is set to zero in all plots.
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Experimental and calculated FT-IR spectra of the powdered RbCoSOH Tutton crystal.
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Experimental and calculated Raman spectra of the powdered RbCoSOH Tutton crystal.
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Simultaneous TG-DSC thermograms of RbCoSOH crystal in powder form.
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UV-vis-NIR absorbance spectrum of a RbCoSOH single crystal. The symbol * indicates the Jahn-Teller effect observed at around 475 nm. Inset: Corresponding optical transmittance spectrum.
See this image and copyright information in PMC

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