Multipolar Porphyrin‐Triazatruxene Arrays for Two‐Photon Fluorescence Cell Imaging

Abstract

Two-photon excitedf luorescent (TPEF) materials are highly desirable for bioimaging applications owing to their unique characteristics of deep-tissue penetration and high spatiotemporal resolution. Herein, by connectingo ne, two, or three electron-deficient zinc porphyrin units to an electron-rich triazatruxene core via ethynyl p-bridges, conjugated multipolar molecules TAT-(ZnP) n (n = 1-3) were developed as TPEF materialsf or cell imaging. The three new dyes presenth igh fluorescence quantum yields (0.40-0.47) and rationally improved two-photon absorption (TPA) properties. In particular, the peak TPAc ross sectiono fTAT-ZnP (436 GM) is significantly largert han that of the ZnP reference (59 GM). The d TPA values of TAT-(ZnP) 2 and TAT-(ZnP) 3 further increase to 1031 and up to 1496 GM, respectively,i ndicatingt he effect of incorporated ZnP units on the TPA properties. The substantial improvemento ft he TPEF properties is attributed to the formation of p-conjugated quadrapole/octupole molecules and the extensiono fD-p-AD systems,w hich has been rationalized by density function theory(DFT) calculations. Moreover, all of the three new dyes displayg ood biocompatibility and preferential targeting ability towardc ytomembrane, thusc an be superior candidates for TPEF imaging of living cells. Overall, this work demonstratedapromisings trategy for the development of porphyrin-based TPEF materials by the construction and extensiono fD-p-AD multipolar array.

A porphyrin-triazatruxene dyad for ratiometric two-photon fluorescent sensing of intracellular viscosity

“…The dyad was synthesized by connecting a triazatruxene unit ( TAT-E ) 22 with a meso -brominated porphyrin derivative ( ZnPor-Br ) via a Sonogashira cross-coupling reaction. 27 The A3B-type intermediate ZnPor-Br was prepared by a cyclic condensation reaction of a benzaldehyde derivative with two different dipyrromethanes, 28 followed by bromination and metalation.…”

“…Furthermore, the rotation about the ethynyl bridge can be modulated by changing the viscosity of media, therefore viscosity responsive fluorescent performance can be expected according to the TICT mechanism. 18 The dyad was synthesized by connecting a triazatruxene unit (TAT-E) 22 with a meso-brominated porphyrin derivative (ZnPor-Br) via a Sonogashira cross-coupling reaction. 27 The A3B-type intermediate ZnPor-Br was prepared by a cyclic condensation reaction of a benzaldehyde derivative with two different dipyrromethanes, 28 followed by bromination and metalation.…”

“…1a and Table S1, ESI †) and almost unaltered. 22 Upon excitation at 350 nm, where the absorption of the TAT moiety dominates, TAT-ZnPor exhibits a blue-green emission band (400-500 nm) and a red emission band (600-750 nm) (Fig. 1b).…”

“…19,20 In this way, sensitive ratiometric responses toward viscosity changes can be achieved. 21 On the other hand, the above mentioned D-p-A configuration for viscosity FMRs is also one of the most important strategies for the design of two-photon excited fluorescent (TPEF) molecules, 22,23 which surpass the one photon excited ones in terms of longer excitation wavelength, deeper tissue penetration, and higher spatial resolution. 24 Herein, by combining the concepts of TICT and TPEF in a D-p-A molecular system, a porphyrin-triazatruxene dyad (TAT-ZnPor) was developed for ratiometric two-photon fluorescent sensing of intracellular viscosity (Scheme 1).…”

“…19,20 In this way, sensitive ratiometric responses toward viscosity changes can be achieved. 21 On the other hand, the above mentioned D-π-A configuration for viscosity FMRs is also one of the most important strategies for the design of two-photon excited fluorescent (TPEF) molecules, 22,23 which surpass the one photon excited ones in terms of longer excitation wavelength, deeper tissue penetration, and higher spatial resolution. 24…”