Rhodium-Catalyzed Synthesis, Crystal Structures, and Photophysical Properties of [6]Cycloparaphenylene Tetracarboxylates

Abstract

The synthesis of C 2-symmetrical [6]­cycloparaphenylene (CPP) tetracarboxylates has been achieved via macrocyclization by the rhodium-catalyzed intermolecular stepwise cross-alkyne cyclotrimerization and subsequent reductive aromatization. The 1H NMR spectra of the thus-obtained C 2-symmetrical [6]­CPP-tetracarboxylates revealed that the rotation of unsubstituted benzene rings is slow at room temperature. These [6]­CPPs formed columnar packing structures, and their absorption maxima were significantly blue-shifted compared to that of nonsubstituted [6]­CPP due to the presence of four electron-withdrawing ester moieties.

Synthesis, Structures, and Properties of Highly Strained Cyclophenylene–Ethynylenes with Axial and Helical Chirality

“…Chemie energy of 3b (120.6 kcal mol À1 )w as significantly larger than those of [16]CPPL (102.7 kcal mol À1 ) [3d] and spiro [8,8]CPP (92.2 kcal mol À1 ). [3e] Thep hotophysical and chiroptical properties of CPEs in dichloromethane are shown in Figure 3a nd the data are summarized in Table 2.…”

Synthesis, Structures, and Properties of Highly Strained Cyclophenylene–Ethynylenes with Axial and Helical Chirality

“…Forschungsartikel energy of 3b (120.6 kcal mol À1 )w as significantly larger than those of [16]CPPL (102.7 kcal mol À1 ) [3d] and spiro [8,8]CPP (92.2 kcal mol À1 ). [3e] Thep hotophysical and chiroptical properties of CPEs in dichloromethane are shown in Figure 3a nd the data are summarized in Table 2.…”

“…Our research group reported the synthesis of [6]cycloparaphenylene [7] tetracarboxylates, [ 6]CPP-(CO 2 R) 4 ,b yt he rhodium-catalyzed [2+ +2+ +2] cycloaddition of U-shaped prearomatic diynes with dialkyl acetylenedicarboxylates followed by reductive aromatization (Figure 1b). [8,9] In this reaction, two ethynyl groups of the U-shaped prearomatic diynes are close to each other, and thus the desired 1:1crosscycloaddition with dialkyl acetylenedicarboxylates proceeded smoothly.B esides the 1 HNMR analysis revealed that all benzene rings of [6]CPP-(CO 2 R) 4 are non-rotatable due to large ring strain. Based on these results,w ea nticipated that the cross-coupling between biphenyl-linked diyne 1a and Ushaped prearomatic diiodoparaphenylene 2 followed by reductive aromatization would also proceed smoothly to give CPE 3a,p ossessing stable axial and helical chirality,a s ar esult of the restricted rotation around the biphenyl and CÀCCÀCa xes [10] due to large ring strain as with [6]CPP (Figure 1c).…”

“…Our research group reported the synthesis of [6]cycloparaphenylene tetracarboxylates, [6]CPP‐(CO 2 R) 4 , by the rhodium‐catalyzed [2+2+2] cycloaddition of U‐shaped prearomatic diynes with dialkyl acetylenedicarboxylates followed by reductive aromatization (Figure b) . In this reaction, two ethynyl groups of the U‐shaped prearomatic diynes are close to each other, and thus the desired 1:1 cross‐cycloaddition with dialkyl acetylenedicarboxylates proceeded smoothly.…”

Theoretical Insights for Materials Properties of Cyclic Organic Nanorings

“…">2.The comprehension of the driving forces for the supramolecular packing and cohesive energies of these systems as a function of their size, [ 107 ] therefore opening a way to tune their supramolecular structure to access solid‐state CNT‐like structures via the adequate functionalization, [ 108–110 ] and the determination of the preferred charge‐transfer career paths [ 111,112 ] ; 3.The differences between pristine and substituted CPPs, [ 113–121 ] with emphasis on intra‐molecular donor‐acceptor compounds [ 122–124 ] displaying fluorescent and semiconducting properties upon specific functionalization [ 125 ] ; 4.The influence of structural units after changing phenylene by pyrenylene (i.e., CycloPYrelenes [CPYs]) or ever larger structural motifs [ 126–128 ] and its effect on the single‐molecule [ 129 ] and supramolecular properties [ 130 ] ; and finally …”