Cyclic 2,12-Porphyrinylene Nanorings as a Porphyrin Analogue of Cycloparaphenylenes

Abstract

β-to-β Directly linked cyclic Ni(II) porphyrin trimer, tetramer, and pentamer ([3]CP, [4]CP, and [5]CP) have been synthesized by reaction of a 2,12-diborylated Ni(II) porphyrin with Pt(cod)Cl2 followed by reductive elimination. The structures of these cyclic porphyrin arrays have been revealed by X-ray diffraction analysis. The strain energies of these cyclic oligomers are calculated to be 77, 57, and 47 kcal/mol for [3]CP, [4]CP, and [5]CP, respectively. Intramolecular excitation energy hopping was observed between the (3)(d,d) states of the Ni(II) porphyrins with rates of 3.0, 4.4, and 4.6 ps for [3]CP, [4]CP, and [5]CP, respectively, reflecting the close proximity of the Ni(II) centers.

Synthesis of [n]Cyclo‐5,15‐porphyrinylene‐4,4′‐biphenylenes Displaying Size‐Dependent Excitation‐Energy Hopping

“…[10] CPB by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS). [8] In line with the symmetrical (D nh ) structures of the [n]CPB nanorings, their 1 Hand 13 CNMR spectra display as ingle set of signals for the porphyrin and biphenylene bridge.I nt he aromatic region of the 1 HNMR spectra of the [n]CPB oligomers ( Figure 1), two doublets due to the porphyrinic b-hydrogen atoms (H c and H d ), two doublets due to the hydrogen atoms of the biphenylene bridge (H a and H b ), and signals due to the aromatic hydrogen atoms of the 3,5-di-tert-butylphenyl groups (H e and H f )a re observed. However, poor yields and low solubility have hampered the isolation of such large wheels,and the yields of [n]CPB wheels with n = 3-6 were even lower under these conditions.N one of the corresponding [n]CPB rings were obtained from either Zn II or free-base porphyrin precursors under similar conditions, thus suggesting that aN i II porphyrin scaffold is of vital importance for the successful formation of porphyrin nanorings,inanalogy with the formation of [n]CP systems.…”

“…[4c] Another strategy makes use of asequence of platinum(II) bridging and reductive elimination. [8] An important factor in these syntheses is ap referred cis geometry of the platinum-bridged nanoring intermediates, which causes molecular curvature as af avorable structural feature for nanoring formation. [8] An important factor in these syntheses is ap referred cis geometry of the platinum-bridged nanoring intermediates, which causes molecular curvature as af avorable structural feature for nanoring formation.…”

Coordination-Driven, Self-Assembly of a Polycyclic, Terpyridine-Based Nanobelt

“…-tpy[ (tpy = [2,2 0 :6 0 ,2 00 ]terpyridine and M = Ru, Fe, Zn or Cd) connectivity to fabricate supramacromolecules has distinct advantages due to the diversity of metal coordination, unique metal-ligand physical properties, rigidity, and ability to incorporate predesigned, structured directionality. Recently, this building protocol has led to the creation of several 2D-and 3D-nano-structures, including bowtie-, butterfly-, and spoke wheel-shaped supramolecules [16][17][18][19]. As well, the porphyrin analogues of [n]cycloparaphenylenes are known [7d].…”

Selective and Gram-Scale Synthesis of [6]Cycloparaphenylene

“…1-8 Since the first syntheses of [9]CPP, [12]CPP, and [18]CPP by Bertozzi and co-workers in 2008, 9 significant progress toward the synthesis of CPPs and CPP analogues of various sizes has been made by Jasti, [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] and their respective co-workers, as well as by other research groups. [36][37][38][39][40][41][42][43] Consequently, several unique properties of CPPs, such as their size-dependent photophysical 44-50 and redox properties 31,51-55 and their size-complementary host-guest chemistries, 56-59 have been revealed.The synthesis of small CPPs has recently attracted significant attention because smaller CPPs possess narrower HOMO-LUMO energy gaps than do larger CPPs, 31 which is advantageous in relation to applications in organic electronic materials. For example, [5]CPP, the smallest CPP synthesized to date, possesses the narrowest HOMO-LUMO gap among known CPPs and it has a similar energy gap to that of buckminsterfullerene.…”

“…[1][2][3][4][5][6][7][8] Since the first syntheses of [9]CPP, [12]CPP, and [18]CPP by Bertozzi and co-workers in 2008, 9 significant progress toward the synthesis of CPPs and CPP analogues of various sizes has been made by Jasti, [9][10][11][12][13][14][15][16] Itami, [17][18][19][20][21][22][23][24][25][26][27][28] Yamago, [29][30][31][32][33][34][35] and their respective co-workers, as well as by other research groups. [36][37][38][39][40][41][42][43] Consequently, several unique properties of CPPs, such as their size-dependent photophysical [44][45]…”