Synthesis, structures and properties of a meso-substituted pyrazolyl porphyrin and its Co(II) porphyrin complex

• One new pyrazole-functionalized porphyrin and Co(II) porphyrin were synthesized and characterized structurally.
• Insertion of Co(II) ion into porphyrin macrocycle leads to a saddle distortion of Co(II) porphyrin plane.
• UV–vis and fluorescent spectra of the two compounds in CH2Cl2 and solid state were compared.
• Co(II)Pp shows high catalytic activities to ethylbenzene oxidation with 83% conversion.

In this work, one new porphyrin, 5, 10, 15, 20-tetrakis(4-N-pyrazolyl)phenyl porphyrin (H2Pp) was synthesized and characterized. The single crystal structures of H2Pp and its cobalt(II) porphyrin (Co(II)Pp) were obtained with a space group of P1− and I2/c, respectively. The porphyrin macrocycle is close to a perfect plane in H2Pp, while Co(II)Pp exhibits a saddle-type distortion due to the formation of shorter Co–N coordination bonds. In H2Pp, the molecules are interconnected through π⋯π and C–H⋯π interactions to form 3D architecture, while in Co(II)Pp the porphyrin molecules are interlinked only by C–H⋯π interactions to yield 3D structure. We examined the UV–vis spectra and fluorescent spectra of H2Pp and Co(II)Pp in CH2Cl2 and solid state at room temperature. In addition, the catalytic activities of Co(II)Pp to the ethylbenzene oxidation was examined, the results indicate that Co(II)Pp exhibits a high selectivity to acetophenone (> 99%) with the conversion of 83%.

In H2Pp, the molecules are interconnected through π⋯π and C–H···π interactions to form 3D structure, while in Co(II)Pp the porphyrin molecules are interlinked only by C–H⋯π interactions to yield 3D structure. Co(II)Pp displays high catalytic activity with the only product acetophenone quantitatively in 83%.Figure optionsDownload as PowerPoint slide