π‐Extended “Earring” Porphyrins with Multiple Cavities and Near‐Infrared Absorption

Abstract

b,b-tripyrrin-bridged earring porphyrins were synthesized through Suzuki-Miyaura cross coupling reactions. These porphyrinoids have multiple cavities and can accommodate two or three metal ions per molecule.The structures of the porphyrins have been elucidated by x-ray diffraction analysis,and feature curved p planes.The electronic spectra of the porphyrins exhibit near-infrared (NIR) absorptions and metal insertion leads to red-shifted and intensified absorption features.E lectrochemical analysis and transient absorption measurements indicated that the porphyrins exhibit effective electronic communication between their central and peripheral moieties.

Benzene- and pyridine-incorporated octaphyrins with different coordination modes toward two PdII centers

“…The key precursor α,α′-Diboryltripyrrane 9 was prepared by regioselective Ir-catalyzed borylation of 5,10dimesityltripyrrane ( Fig. 2) 28 . Firstly, we tried the synthesis of 1,3phenylene-incorporating octaphyrin 12 by Suzuki-Miyaura coupling of 9 with m-dibromobenzene and subsequent oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) but this reaction sequence gave linear precursor 10 in 53% yield.…”

“…Recently we explored various porphyrinoids by using Suzuki-Miyaura coupling. Reported examples include cyclic porphyrin rings, BODIPY-porphyrin hybrids, and earring porphyrins [24][25][26][27][28] . Despite of these studies, we thought that this coupling strategy could be applied to the synthesis of pyridine-incorporated expanded porphyrins.…”

Multi‐Cation Coordination in Porphyrinoids

“…Ad ifferent approach for formation of structures involving a meso-position as ad onor has been reported by Song and coworkers where the additional cavity has been created (Scheme9). [21] In this approach dibromo derivative 36 coupled with diborylated tripyrrane 21 eventually gave as keleton with additional cavity 37. 37 opens ap ossibility of extendingt he delocalisation from 18p path characteristic for aromatic tetraphyrin(1.1.1.1) to 28p electrons potentially showing an antiaromatic character.T he analysiso f 1 HNMR spectra as well as NICS calculations (a = À14.47 ppm; b =+10.47 ppm) indicate that p-cloudso ft wo macrocyclic loops do not tend to extend over the entire molecule with the parentt etraphyrinr emaining aromatic structure with the attached triphyrin(5.1.1) motif showing an antiaromatic circuit.…”

“…The additional stabilization has been observed for apalladium(II) complex 38 where the 18p electrons path dominates. [21] The scope of tested reactivity was expanded to porphyrins bearing two triphyrin(5.1.1) motifs that wasa ble to bind two palladium(II) cations in both CNNN coordination sites forming 39 (Figure 3). Both palladium(II)c omplexes 38 and 39 show NIR absorption from 700 to 1500 nm suggesting improved orbital overlap caused by binding to as izeable transition metal.…”

“…Both palladium(II)c omplexes 38 and 39 show NIR absorption from 700 to 1500 nm suggesting improved orbital overlap caused by binding to as izeable transition metal. [21] Furthere xploration of 'earring porphyrin" concept by the same research group resulted in obtaining molecules where tetraphyrina nd triphyrin motifs are additionally fused by heterole (thiphene, pyrrole) units (Figure 4). [22] The fusion caused significant changes in av alue of chemical shifts.Ac arbatriphyrynic b-pyrrolic protons in 40 a resonate at incredibly low-frequency region (d:3 .51, 3.36 ppm vs. 6.76-5.37 ppm in 38).…”