title: Snapshotting the Excited-State Planarization of Chemically Locked N,N'-Disubstituted Dihydrodibenzo[a,c]phenazines.
abstract: For deeper understanding of the coupling of electronic processes with conformational motions, we exploit a tailored strategy to harness the excited-state planarization of N,N'-disubstituted dihydrodibenzo[a,c]phenazines by halting the structural evolution via a macrocyclization process. In this new approach, 9,14-diphenyl-9,14-dihydrodibenzo[a,c]phenazine (DPAC) is used as a prototype, in which the para sites of 9,14-diphenyl are systematically enclosed by a dialkoxybenzene-alkyl-ester or -ether linkage with different chain lengths, imposing various degrees of constraint to impede the structural deformation. Accordingly, a series of DPAC-n (n = 1-8) derivatives were synthesized, in which n correlates with the alkyl length, such that the strength of the spatial constraint decreases as n increases. The structures of DPAC-1, DPAC-3, DPAC-4, and DPAC-8 were identified by the X-ray crystal analysis. As a result, despite nearly identical absorption spectra (onset ∼400 nm) for DPAC-1-8, drastic chain-length dependent emission is observed, spanning from blue (n = 1, 2, ∼400 nm) and blue-green (n = 3-5, 500-550 nm) to green-orange (n = 6) and red (n = 7, 8, ∼610 nm) in various regular solvents. Comprehensive spectroscopic and dynamic studies, together with a computational approach, rationalized the associated excited-state structure responding to emission origin. Severing the linkage for DPAC-5 via lipase treatment releases the structural freedom and hence results in drastic changes of emission from blue-green (490 nm) to red (625 nm), showing the brightening prospect of these chemically locked DPAC-n in both fundamental studies and applications.
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology , Shanghai 200237, P. R. China.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, 10617 Taiwan, R.O.C.
authors.forename: Chi-Lin
authors.initials: CL
authors.lastname: Chen
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology , Shanghai 200237, P. R. China.|Department of Chemistry, National Taiwan University , Taipei, 10617 Taiwan, R.O.C.
authors.forename: Zhiyun
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, 10617 Taiwan, R.O.C.
authors.forename: Yi-An
authors.initials: YA
authors.lastname: Chen
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, 10617 Taiwan, R.O.C.
authors.forename: Wei-Chih
authors.initials: WC
authors.lastname: Chao
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology , Shanghai 200237, P. R. China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Su
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology , Shanghai 200237, P. R. China.
authors.forename: He
authors.initials: H
authors.lastname: Tian
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei, 10617 Taiwan, R.O.C.
authors.forename: Pi-Tai
authors.identifier: 0000-0002-8925-7747
authors.initials: PT
authors.lastname: Chou