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N^N^C-Cyclometalated rhodium(III) complexes with isomeric pyrimidine-based ligands: unveiling the impact of isomerism on structural motifs, luminescence and cytotoxicity.
- Source :
- Dalton Transactions: An International Journal of Inorganic Chemistry; 5/21/2024, Vol. 53 Issue 19, p8398-8416, 19p
- Publication Year :
- 2024
-
Abstract
- The impact of isomerism of pyrimidine-based ligands and their rhodium(III) complexes with regard to their structures and properties was investigated. Two isomeric ligands, 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2,5-diphenylpyrimidine (HL<superscript>2,5</superscript>) and 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2,6-diphenylpyrimidine (HL<superscript>2,6</superscript>), were synthesized. The ligands differ by the degree of steric bulk: the molecular structure of HL<superscript>2,5</superscript> is more distorted due to presence of pyrazolyl and phenyl groups in the neighbouring positions 4 and 5 of the pyrimidine ring. The complexation of HL<superscript>2,5</superscript> and HL<superscript>2,6</superscript> with RhCl<subscript>3</subscript> leads to the sp<superscript>2</superscript> C–H bond activation, resulting in the isolation of two complexes, [RhL<superscript>2,5</superscript>(Solv)Cl<subscript>2</subscript>]·nEtOH and [RhL<superscript>2,6</superscript>(Solv)Cl<subscript>2</subscript>]·nEtOH (Solv = H<subscript>2</subscript>O, EtOH), with the deprotonated forms of the pyrazolylpyrimidine molecules which coordinate the Rh<superscript>3+</superscript> ion as N^N^C-tridentate ligands. According to DFT modelling, the mechanism of the deprotonation involves (i) the C–H bond breaking in the 2-phenyl group followed by the coordination of the C atom to the Rh atom, (ii) the protonation of coordinated chlorido ligand, (iii) the ejection of the HCl molecule and (iv) the coordination of the H<subscript>2</subscript>O molecule. The ligand isomerism has an impact on emission properties and cytotoxicity of the complexes. Although the excited states of the complexes effectively deactivate through S<subscript>0</subscript>/T<subscript>1</subscript> and S<subscript>0</subscript>/S<subscript>1</subscript> crossings associated with the cleavage of the weak H<subscript>2</subscript>O ligands upon excitation, the [RhL<superscript>2,5</superscript>(Solv)Cl<subscript>2</subscript>]·nEtOH complex appeared to be emissive in the solid state, while [RhL<superscript>2,6</superscript>(Solv)Cl<subscript>2</subscript>]·nEtOH is non-emissive at all. The complexes show significant cytotoxic activity against cancerous HepG2 and Hep2 cell lines, with the [RhL<superscript>2,6</superscript>(Solv)Cl<subscript>2</subscript>]·nEtOH complex being more active than its isomer [RhL<superscript>2,5</superscript>(Solv)Cl<subscript>2</subscript>]·nEtOH. On the other hand, noticeable cytotoxicity of the latter against HepG2 is supplemented by its non-toxicity against non-cancerous MRC-5 cells. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 14779226
- Volume :
- 53
- Issue :
- 19
- Database :
- Complementary Index
- Journal :
- Dalton Transactions: An International Journal of Inorganic Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 177400800
- Full Text :
- https://doi.org/10.1039/d4dt00824c