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SYNTHESIS AND STRUCTURE OF 2,3-DIHYDROXYL-5-
CARBOXYLBENZENESULFONIC ACID SUPRAMOLECULAR
COMPLEX WITH HEXA-AQUA COBALT COMPLEX
Abror Kh.Ruzmetov
1
Aziz B.Ibragimov
1
Jurabek B.Yuldashev
2
1
Institute of General and Inorganic Chemistry, Uzbekistan
Academy of Sciences, 100170,
Kh.Abdullaev Str., 77a, Tashkent, Uzbekistan
2
Academic Lyceum of the Tashkent Medical Academy, 100109, Shikopar street
3, Almazar district, Tashkent, Uzbekistan
https://doi.org/10.5281/zenodo.14506721
The novel arenesulfonic acid, featuring three functional groups – carboxyl
(–CO₂H), sulfonic acid (–SO₃H), and hydroxyl (–OH) – specifically 2,3-dihydroxy-
5-carboxybenzenesulfonic acid, was synthesized by Ge et al. in 2018 [1]. The
goal of this synthesis was to develop lithium(I)-based metal-organic frameworks
(MOFs) with potential applications in areas such as photochemistry,
electrochemistry, sensors, catalysis, and especially in gas storage and small
molecule separations. The authors successfully obtained two structurally
characterized complexes with both discrete and polymeric configurations.
However, the exact structure of the ligand itself has not yet been determined.
This study focuses on the characterization of the 2,3-dihydroxy-5-
carboxybenzenesulfonic acid (anion) structure as part of its supramolecular
complex (salt) with the hexaaqua cobalt cation (Fig. 1.).
Figure 1.
The molecular structure of the supramolecular compound.
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Structural Commentary: The crystal structure of the title compound is
composed of three main components: 2,3-dihydroxy-5-carboxybenzenesulfonic
acid, a hexaaqua cobalt complex, and an additional water molecule (Fig. 1).
Together, these form a supramolecular complex in salt form, where the sulfonic
acid fragment (anion) is deprotonated to balance the positive double charge of
the cobalt ion (cation). The cobalt ion sits at an inversion center within the P-1
space group of the crystal, leading to three coordinated water molecules in the
asymmetric unit. The overall chemical formula of this supramolecular complex
is [Co(H₂O)₆]∙2(C₇H₅O₇S)∙2(H₂O).
The cobalt–oxygen bond lengths are nearly identical, ranging between
2.0810(14) and 2.0924(15) Å. The bond angles around the cobalt ion vary from
94.54(5)° to 85.47(5)°, giving rise to a slightly distorted octahedral geometry
around the metal center.
Synthesis method: First, 237 mg (0.1 mmol) of CoCl₂ • 6H₂O was dissolved
in 10 ml of MCN. Afterward, 46.8 mg (0.2 mmol) of 2,3-dihydroxy-5-
carboxybenzenesulfonic acid powder was added to the solution, which was
stirred for one hour at 40°C. A clear, light red solution appeared after stirring,
which was then transferred to a flat-bottom beaker with small holes to enable
slow evaporation at room temperature. After one month, red crystals suitable
for X-ray analysis of the compound were obtained with a 48% yield. The crystals
were collected, rinsed with acetone, and dried under vacuum.
Elemental analysis: The elemental composition of the compound
C₁₄H₂₆CoO₂₂S₂ was determined using a Thermo Scientific FlashSmart (CHNS/O)
elemental analyzer, following the gas chromatographic separation of
combustion gases through a modified Dumas method. The elemental analysis of
the compound C₁₄H₂₆CoO₂₂S₂ (Mr = 669.4 g/mol) showed the following
theoretical and practical values: Theoretical carbon (C) content was 25.1%,
while the practical value was 24.617%; for hydrogen (H), the theoretical content
was 3.884%, compared to the practical result of 3.684%; sulfur (S) had a
theoretical value of 9.56%, with a practical value of 9.263%; and oxygen (O)
showed a theoretical content of 52.58%, compared to a practical result of
52.17%.
Aknowledgements: Authors gratefully acknowledge the Ministry of Higher
Education, Science and Innovation for the financial support (project number F3-
20200929348).
References:
Ge, Z.-Y. et al. (2018) “Structure evolution and luminescence properties of
lithium(i)–sulfonate
complexes
constructed
from
multifunctional
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arenedisulfonic acids”, CrystEngComm, 20(21), bll 2968–2979. doi:
10.1039/C8CE00224J.
