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Click Reaction Synthesis and Photophysical Studies of Dendritic Metalloporphyrins
Author(s) -
Nguyen Nguyen Tran,
Hofkens Johan,
Scheblykin Ivan G.,
Kruk Mikalai,
Dehaen Wim
Publication year - 2014
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201301158
Subject(s) - dendrimer , chemistry , carbazole , photochemistry , quantum yield , steric effects , porphyrin , click chemistry , aryl , azide , luminescence , fluorescence , phosphorescence , polymer chemistry , stereochemistry , organic chemistry , materials science , physics , alkyl , optoelectronics , quantum mechanics
Abstract Several dendritic zinc(II)‐porphyrins bearing carbazole units at the terminals have been prepared through click reaction of azide‐substituted Zn‐porphyrin precursors and carbazole‐based alkynes under [Cu(NCCH 3 ) 4 ][PF 6 ] catalysis. This family of new dendritic metalloporphyrins shows dual luminescence from both the upper S 2 and the lowest S 1 singlet states. The observed trends in the spectroscopic data and the photophysical properties of the dendrimers have been rationalized in terms of the type of meso ‐spacer between the macrocycle and dendritic shell. The key feature of the meso ‐spacer is proposed to be the degree of hindrance towards aryl ring rotation relative to the mean porphyrin plane. Based on the observed differences in the S 1 →S 0 fluorescence quantum yield on going from four‐ to five‐coordinate dendrimers, it was shown that dendrimer architectures with all four meso ‐aryl spacers sterically hindered, are most appropriate to monitor processes related to axial ligation of the dendrimer core, since they provide larger luminescence response differences between the four‐coordinate and five‐coordinate forms. The blue S 2 →S 0 fluorescence quantum yield has been measured and the observed trend has been rationalized in terms of the S 2 →S 1 energy gap law. No significant differences were observed between the compounds either with different rotational degree of freedom of the meso ‐spacers or with different ligation states of the dendrimer core.