Metal-organic architectures driven by a multifunctional 6-aminouracil spacer: Structures, noncovalent interactions, and conductivity

Three new coordination polymers, [NaI(H2L)(H2O)3]n (1), {[KI(H2L)(H2O)]8·13H2O}n (2), and {[NiIINaI2(HL)2(H2O)8]·6H2O}n (3), were assembled from 1,3-dimethyl-5-(p-sulfonic-phenylazo)-6-aminouracil (H3L) as a versatile building block. Although azo-coupling reactions generally result in simple azo-compounds, the presence of the sulfonate (-SO3-) group at the ligand frame led to the formation of the NaI-1D (1) or KI-3D (2) homometallic coordination polymer with different ligand coordination modes. Moreover, the heterometallic NiII/NaI-1D (3) coordination polymer was obtained while carrying the reaction of 2 with NiCl2·6H2O. The structures of the obtained products were fully established by single crystal X-ray diffraction and confirmed by standard methods. Compounds 1 and 3 possess 1D metal-organic chains with the 2C1 topology, whereas 2 features a very complex 3D metal-organic architecture with an unprecedented topology. The computational study for molecular electrostatic potential (MEP) surface energies revealed an important finding, namely a decrease of the π-acidity of the uracil ring upon coordination and a consequent increase of the π-basicity of the phenyl-sulfonate ring, resulting in effective anti-parallel π-π stacking interactions in 1 and 2. Finally, a semi-conductive behavior of the obtained compounds was explored using impedance spectroscopy, revealing the very remarkable conductive properties of 1 (2.2 × 10-4 S cm-1), which is a far better conductive material than 2 (7.2 × 10-6 S cm-1) and 3 (4.8 × 10-7 S cm-1). The obtained products represent the first coordination compounds derived from H3L. This study contributes to the design of functional coordination polymers driven by still poorly explored 6-aminouracil building blocks. © 2020 The Royal Society of Chemistry.

Purkayastha A.1 , Dhar S.2 , Mondal S.P.2 , Franconetti A.3 , Frontera A.3 , Ganguly R.4 , Kirillov A.M. 5, 6 , Misra T.K.1
Royal Society of Chemistry
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  • 1 Department of Chemistry, National Institute of Technology, Agartala, Tripura, 799046, India
  • 2 Department of Physics, National Institute of Technology, Agartala, Tripura, 799046, India
  • 3 Departamento de Química, Universitat de les Llles Balears, Crta. de Valldemossa, 07122, Spain
  • 4 Division of Chemistry and Biological Chemistry, Nanyang Technology University, Singapore, 639798, Singapore
  • 5 Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1049-1005, Lisbon, Portugal
  • 6 Research Institute of Chemistry, Peoples' Friendship University of Russia (RUDN University), 6 Miklukho-Maklaya St., Moscow, 117198, Russian Federation
Conductive materials; Ions; Ligands; Nickel compounds; Organometallics; Single crystals; Topology; Azo coupling reactions; Coordination compounds; Functional coordination; Impedance spectroscopy; Metal-organic architecture; Molecular electrostatic potentials; Non-covalent interaction; Single crystal x-ray diffraction; Polymers
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