Cyclic Carbaporphyrin Arrays

Abstract

Two cyclic carbaporphyrin arrays (trimer 6 and tetramer 7) were synthesized from a dibrominated carbaporphyrin precursor (5) via a one-pot Yamamoto-type coupling. Single-crystal X-ray diffraction analyses revealed that 6 and 7 contain three and four covalently linked carbaporphyrin (formally dicarbacorrole) units, respectively. Trimer 6 adopts a roughly planar conformation and tetramer 7 adopts an up-and-down zig-zag conformation. Both 6 and 7 contain a [n]cyclo-meta-phenylene ([n]CMP) core, namely, [6]-and [8]CMP for 6 and 7, respectively. Transient absorption (TA) anisotropy and pump-power-dependent excitedstate decay studies provided evidence for excitation energy transfer (EET) within both trimer 6 and tetramer 7. The exciton energy hopping (EEH) times were estimated to be 18 and 35 ps for 6 and 7, respectively, as inferred from pump-power-dependent TA measurements. Since the center-to-center distances between adjacent carbaporphyrin units are similar in 6 and 7, the different EEH times are attributed to differences in the orientation of the transition dipoles in these two congeneric arrays. The orientation factor κ 2 , the key parameter defining the Forster resonance energy transfer efficiency, was calculated to be 2.15 and 1.03 for 6 and 7, respectively, a finding that supports the shorter excitation energy hopping time seen in the case of trimer 6. To our knowledge, this is the first time that covalently linked cyclic carbaporphyrin arrays were synthesized using a single carbaporphyrin as the starting point and that EET between carbaporphyrin subunits constrained within a well-defined polycyclic framework has been correlated with structural differences.

Functionalization of Pentacene: A Facile and Versatile Approach to Contorted Polycyclic Aromatic Hydrocarbons

“…Therefore, the prevalent strategies for the synthesis of such contorted and highly fused π‐conjugated systems are usually confronted with the problems of multi‐step synthesis, tedious purification processes and relatively low yields. But then contorted PAHs can bring up a lot of interesting physical and chemical characteristics such as chiroptical properties and the intramolecular ring‐closure reaction [33–49] . Thus, the pursuit of the new and more concise synthesis of contorted polycyclic aromatic hydrocarbons with unprecedented carbon structures and advanced functions remains a subject of unfailing charm for synthetic chemists [50–53] …”

Elucidating the Excited State Behavior of Pyridyl Pyridinium Systems via Computational and Transient Absorption Studies of Tetrahedral Multichromophoric Arrays and their Model Compounds

“…In order to clarify how the spatial arrangement affects the properties of the whole system, it is essential to compare the chemical and photophysical properties of the individual chromophoric units with those of the multichromophoric arrays. [5,6,7] Pyridinium and bipyridinium chromophores (the latter also known as viologens, namely, 1,1'-disubstituted-4,4-bipyridinium salts) are extensively studied for their remarkable photochem-ical and electrochemical properties. [8] They have been explored as components for molecular batteries, electrochromic displays, redox mediators and redox sensors.…”

“…Notably, this arrangement allows a precise control of the interchromophoric distance and the relative orientation of the chromophores. In order to clarify how the spatial arrangement affects the properties of the whole system, it is essential to compare the chemical and photophysical properties of the individual chromophoric units with those of the multichromophoric arrays [5,6,7] …”

Functionalization of Pentacene: A Facile and Versatile Approach to Contorted Polycyclic Aromatic Hydrocarbons

“…Therefore, the prevalent strategies for the synthesis of such contorted and highly fused π‐conjugated systems are usually confronted with the problems of multi‐step synthesis, tedious purification processes and relatively low yields. But then contorted PAHs can bring up a lot of interesting physical and chemical characteristics such as chiroptical properties and the intramolecular ring‐closure reaction [33–49] . Thus, the pursuit of the new and more concise synthesis of contorted polycyclic aromatic hydrocarbons with unprecedented carbon structures and advanced functions remains a subject of unfailing charm for synthetic chemists [50–53] …”

“…But then contorted PAHs can bring up a lot of interesting physical and chemical characteristics such as chiroptical properties and the intramolecular ring-closure reaction. [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] Thus, the pursuit of the new and more concise synthesis of contorted polycyclic aromatic hydrocarbons with unprecedented carbon structures and advanced functions remains a subject of unfailing charm for synthetic chemists. [50][51][52][53] Pentacene, consisting of linearly fused benzene rings, exhibits unique optical, electronic, and chemical properties that have long been appreciated and exploited.…”