Design, Synthesis And Properties Of Carbazole-based Two-photon Fluorescent Probes

In recent years, fluorescent probe, with high sensitivity and selectivity, is regarded as an effective biological detective tool, because it is able to conduct real-time detection and easy to operate. Most fluorescent probes being reported so far are single photon fluorescent probes. There are many drawbacks due to the fact that single photon fluorescent probes are activated by short wavelength. For instance, single-photon fluorescent probes are highly likely to give rise to photo damage, photo-bleaching and background color. In consequence, in order to overcome the drawbacks of single photon fluorescent probes, it is necessary for us to seek two-photon fluorescent probes with larger absorption cross-section and more sensitive detection, which is activated by long wavelength, is capable of being used in cells and is equipped with higher fluorescence quantum yield. Hypochloric acid, one of the important reactive oxygen species in organisms, is endowed with oxidability, which casts tremendous influences upon organisms and is widely used in daily life. However, excessive hypochloric acid will causes some diseases, such as cancer. Gold is a kind of precious medal, which can be used to make currency, jewelry and accessories. Moreover, gold ion, which is anti-inflammatory, can be used to make medicine for arthritis and cancer.Even though gold ion can be used in so many ways, we should also attach importance to its formidable toxicity, since it can combine with DNA intimately, doing damage to liver, kidney and the nervous system. As a result, we ought to lay control over the content of gold ions. Cu is a significant transitional metals, only secondary to Fe and Zn, and plays an indispensable role in maintaining the normal function of organisms. Even though there are few Cu2+ ions in organisms, lack of Cu2+ ions will cause disturbance to organisms growth process. Similarly, excessive Cu2+ ions will also intoxicate organisms. In consequence, it has been an important issue for biological and medical research to detect the content of hypochloric acid, gold ions and copper ions in organisms and study the dynamic distribution of hypochloric acid, gold ions and copper ions in living cells. On the basis of reviewing a large amount of literature, carbazole-based two-photon fluorescent probes were designed and synthesized, which can be capable of selectively recognizing ClO-, Au3+, Cu2+. We characterized the structure of targe probes by virtue of such tests as 1H NMR,13C NMR and mass spectrometric measurement, and studied optical properties via ultraviolet and one/two photon fluorescence, some of which has been successively used in cell imaging and to locate mitochondria.First of all, we have designed two water-soluble hypochloric acid two-photon fluorescent probes taking carbazole as the matrix. The reason for taking carbazole as the matrix resides in that the already reported carbazole fluorescent probes show such advantages as excellent photo-stability, low cell toxicity and large two-photon absorption cross-section. D-Ï€-A two-photon fluorescent probes are made by taking carbazole group as electron donor and taking pyridine cations as electron acceptor. This prominent intramolecular charge transfer (ICT) ensures the two-photon characteristics of probes. Oxime as a recognition group, by C= N bond rotation in order to achieve the detection of hypochlorous acid. Pyridine cations can be located in mitochondria and can increase the water-solubility of probes.Secondly, based on the first task and relevant literature, we have made a new two-photon fluorescent probe used for detecting gold ions by taking carbazolyl group as electron donor and taking vinyl pyridine cations as electron acceptor.2-pyridyl hydrazine as a recognition group, to achieve the detection of metal ions by hydrolysis of metal ions. This probe is endowed with high sensitivity, low detection limit and large Stokes displacement, and can be located in mitochondria successively.Finally, we have designed "turn-on" copper ion two-photon fluorescent probes taking carbazole as the matrix. This probe is equipped with brilliant photo-stability, low cell toxicity and large two-photon absorption cross-section.2-Picolinyl hydrazide was chosen as a chelating moiety of Cu2+, which were easily conjugated with the carbazole-based fluorophore by the formation of C=N bond, by hydrolysis of copper and succeeded in detecting copper ions.