Synthesis, coordination chemistry and photophysical properties of naphtho-fused pyrazole ligands

Hawes, Chris S.

Abstract

The synthesis of two p-extended pyrazole ligands is reported, with naphtho[2,1-d]-1H-pyrazole HL1 prepared in a modified Jacobson indazole synthesis from 1-amino-2-methylnaphthalene, and subsequent arylation with 2-bromopyridine giving the chelating ligand N-(2-pyridyl)-naphtho[1,2-c]pyrazole L2 as a single isomer, with both species crystallographically characterised. Each forms mononuclear complexes with Cu2+ and Zn2+; in [Cu(HL1)4(NO3)2] 1 and [ZnCl2(HL1)2] 2 the propensity for outer-sphere hydrogen bonding from the pyrazole N-H group supplements the extended p backbone in influencing crystal packing interactions. The equivalent complexes of the chelating L2, [Cu(L2)(NO3)2] 3 and [ZnCl2(L2)] 4, both show distortion at the coordination sphere caused by the close approach of the hydrogen atom at the naphthyl 8-position, and crystal packing in both instances is dictated purely by the flat aromatic backbone of the ligand. Stability constants for complexes 3 and 4 are determined spectroscopically, and photophysical studies reveal fluorescence with vibrational progressions in both the solution and solid state for each ligand and the zinc complexes 2 and 4.

Citation

Hawes, C. S. (2019). Synthesis, coordination chemistry and photophysical properties of naphtho-fused pyrazole ligands. CrystEngComm, 5152-5163. https://doi.org/10.1039/c9ce01074b

• Acceptance Date: Jul 30, 2019
• Publication Date: Sep 14, 2019
• Journal: CrystEngComm
• Publisher: Royal Society of Chemistry
• Pages: 5152-5163
• DOI: https://doi.org/10.1039/c9ce01074b
• Keywords: coordination chemistry ; photophysical properties ; pyrazole ligands
• Publisher URL: http://doi.org/10.1039/c9ce01074b