Change in supramolecular networks through in situ esterification of porphyrins

A series of porphyrins, M[TCPP-Et₄] [M = Zn (1), Cu (2), and Ni (3) Et = CH₂CH₃; TCPP = meso-tetra(4-carboxyphenyl) porphyrin], M[TCPP-Me₄] [M = Zn (4), Cu (S), and Co (6); Me = CH ₃], and two nonmetalated compounds, TCPP-Et₄ (7) and TCPP-Me₄·H₂O (8), were synthesized by solvothermal reactions and characterized by single-crystal X-ray diffraction. Compounds 1-3 feature an isolated structure with a planar macrocycle and an embedded metal-ion coordinating to four pyrrole nitrogen atoms. Compound 4 is characterized as a two-dimensional coordination polymer, and the zinc ion coordinates to four nitrogen atoms and two oxygen atoms. Compound 4 possesses a large void space (361 ų), which corresponds to 1.4% of the unit-cell volume. Compounds 5 and 6 are characteristic of an isolated motif with a four-coordinate metal ion and a saddle-distorted nonplanar porphyrin macrocycle. Nonmetalated compounds 7 and 8 also show an isolated structure with a planar macrocycle. For compounds 1-3 and 7, the TCPP is esterified with ethanol, while for compounds 4-6 and 8, the TCPP is esterified with methanol. The molecules in 1 and 6-8 are interconnected by hydrogen bonds and π-π interactions to yield 3D supramolecular networks, while in 2-5, 2D supramolecular motifs are formed. The reaction mechanism, was explored. Esterification plays an important role in changing the properties of the compounds as well as in the formation of different structural motifs and supramolecular networks. The UV/Vis, FTIR, fluorescence, phosphorescence, and MALDI-TOF MS spectra, quantum, yields, luminescence lifetimes, and cyclic voltammograms were also studied in detail.