Syntheses and coordination of linear and macrocyclic pentapyrroles possessing a fused moiety: Confusion modulated structural diversityShow others and affiliations
2024 (English)In: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 223, article id 111948Article in journal (Refereed) Published
Abstract [en]
Porphyrinoids have attracted wide interest because of their vital roles in biological processes and fascinating structural and functional characters. In this work, a doubly N-confused pentapyrrane precursor N2C-P5 has been synthesized with terminal pyrrole ring A and middle pyrrole C incorporated in the N-confused mode. On this basis, pentapyrrin 1 and sapphyrin 2 have been synthesized by oxidizing N2C-P5 with 2,3-dichloro-5,6-dicyano1,4-benzoquinone (DDQ). Both 1 and 2 possess a [5.5.5]-tricyclic fused ring involving pyrrole B and the neighboring confused pyrrole C. Meanwhile, the formation of 2 involves ring closure between the terminal rings A and E. Notably, 2 exists as a diradical showing a half-field signal in the electron paramagnetic resonance (EPR) spectrum and a singlet ground state with a negative singlet-triplet energy gap of -0.50 kcal/mol. Excellent thermal stability has been observed for 2, which may be related to its large pi-conjugated framework involving the fused structure. On this basis, 1 and 2 were treated with Cu(acac)2 to afford Cu(II) complexes 3 and 4, respectively. As a result, an acetylacetonyl moiety is attached at the terminal pyrrole ring E to afford an NNNO coordination environment for complex 3, and the sapphyrin macrocycle of 2 has been cleaved between rings A and B to afford a fused pentapyrrin ligand, furnishing an NNNN coordination environment for complex 4, in which a pentafluorophenyl-ketal group generated during the ring cleavage reaction is attached to ring A, and it can be hydrolyzed to the corresponding pentafluorobenzoyl substituent to afford complex 5. Compared with free bases 1 and 2, complexes 3-5 show more intense low-energy near-infrared (NIR) absorption bands at ca. 791, 926 and 907 nm, respectively. This work provides an effective approach for the syntheses of linear and macrocyclic oligopyrroles with intriguing structures and properties by oxidizing oligopyrranes with precisely designed numbers and positions of N-confused pyrroles.
Place, publisher, year, edition, pages
ELSEVIER SCI LTD , 2024. Vol. 223, article id 111948
Keywords [en]
Porphyrinoids; Oligopyrrins; Diradicals; Coordination; Near infrared absorption
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-201451DOI: 10.1016/j.dyepig.2024.111948ISI: 001166642200001OAI: oai:DiVA.org:liu-201451DiVA, id: diva2:1843486
Note
Funding Agencies|NSFC [22131005, 21971063, 22201074, 22075077]; Shanghai Rising -Star Program [23QA1402100]; Natural Science Foundation of Shanghai [23ZR1415600, 22ZR1416100]; Swedish Research Council [2018-05973, 2020-04600]
2024-03-112024-03-112024-03-11