A Novel Porphyrin-Based Ligand Containing Four 4,4′-Dipyridylamine Moieties: Syntheses, Structures, and Luminescent Properties of Mn(II), Cu(II), Zn(II), and Cd(II) Coordination Polymers

The design and syntheses of porphyrin-based ligands are attractive for creating coordination assemblies with novel structures and intriguing properties. In this work, we designed and synthesized a novel porphyrin-based ligand 5,10,15,20-tetrakis­(4,4′-dipyridylaminophenylene)­porphyrin (TDPAP, H₂L) by the introduction of four peripheral 4,4′-dipyridylamine moieties to a porphyrin platform. Starting from this novel ligand, the protonated form of the ligand H₄LCl₂·2CH₃OH­·2H₂O (1) and four coordination polymers [Mn­(III)­Mn­(II)­LCl₃­(DMF)]_n (2), [Cu₄L­(CH₃COO)₅­(HCOO)­(CH₃COOH)­(H₂O)₃]_n­·nCH₃COOH­·nH₂O (3), [Zn₃L­(CH₃COO)₄]_n (4), and [Cd₂H₂L­(CH₃COO)₄]_n­·nDMF­·nCH₃COOH­·2nH₂O (5) were synthesized. Single crystal X-ray diffraction analyses revealed that a rich structural diversity was observed for these compounds due to the coordination of the multiple peripheral pyridines as well as the porphyrin core. 1 displays a hydrogen bonded one-dimensional (1D) structure composed of [(H₂O)₂Cl₂]^2– moieties. Complex 2 shows interpenetrated two-dimensional (2D) coordination networks, which are further linked by π···π stacking interactions to afford a three-dimensional (3D) structure. 3 shows a 2D sheet composed of 50- and 70-membered metallomacrocycles. In complex 4, 1D zigzag coordination chains were generated and further linked to form a 2D structure. Complex 5 has a stairlike 2D structure formed by the linkage of 1D coordination chains through the bridging of binuclear [Cd₂(CO₂)₄] subunits. In these compounds, TDPAP shows a unique coordination behavior. It may bind 4–7 metal centers, and it demonstrates conformational flexibility and the ability to form intermolecular hydrogen bonds and π···π interactions, which contribute to the formation of novel supramolecular structures. On the basis of the novel structures, the solid state emissions of the compounds were also investigated.