Tale of Three Dithienylethenes: Following the Photocycloreversion with Ultrafast Spectroscopy and Quantum Dynamics Simulations.

Photocycloreversion reactions of three diarylethene derivatives whose structures differ only in the placement of two sulfur atoms in the cyclopentene rings are investigated. Despite the minuscule differences between the molecules, both the yields and times of the photoreactions vary considerably. Using UV-vis and infrared femtosecond spectroscopy and quantum chemical dynamics simulations, we elucidate the relationships among the quantum yield, electronic and vibrational relaxation time, and structural properties of the dithienylethene photoswitches.

Wide-range IR spectra of diarylethene derivatives and their simulation using the density functional theory.

Diarylethenes (DAEs), promising photochromic molecular switches, undergo pericyclic reactions upon ultraviolet or visible light illumination. For this reason, most studies on DAEs employ UV-vis spectroscopies. However, also their infrared (IR) spectra are valuable, in particular, for understanding the vibrational dynamics which accompanies the relevant photoreactions.

Zinc Phthalocyanine Photochemistry by Raman Imaging, Fluorescence Spectroscopy and Femtosecond Spectroscopy in Normal and Cancerous Human Colon Tissues and Single Cells.

Photodynamic therapy is a clinically approved alternative method for cancer treatment in which a combination of nontoxic drugs known as photosensitizers and oxygen is used. Despite intensive investigations and encouraging results, zinc phthalocyanines (ZnPcs) have not yet been approved as photosensitizers for clinical use. Label-free Raman imaging of nonfixed and unstained normal and cancerous colon human tissues and normal human CCD18-Co and cancerous CaCo-2 cell lines, without and after adding ZnPcS photosensitizer, was analyzed.

A deeper look into the photocycloreversion of a yellow diarylethene photoswitch: why is it so fast?

Although photoreaction quantum yields of photoswitches determine their switching efficiency, the rates of those reactions are essential parameters because they can establish the eventual temporal resolution of the device using the switch. 1,2-Bis(3,5-dimethylthiophen-2-yl)hexafluorocyclopentene (DMT) features efficient photochromic reactions of both ring-opening and closure and a markedly short time constant of the ring-opening reaction. We have found that the latter is due to the fact that the electronic relaxation from the S state of the closed-ring isomer of DMT occurs through a single dissipation channel, leading to a conical intersection in which the DMT molecule possesses open-ring-like geometry.

A look into the use of Raman spectroscopy for brain and breast cancer diagnostics: linear and non-linear optics in cancer research as a gateway to tumor cell identity.

: Currently, intensely developing of linear and non-linear optical methods for cancer detection provides a valuable tool to improve sensitivity and specificity. One of the main reasons for insufficient progress in cancer diagnostics is related to the fact that most cancer types are not only heterogeneous in their genetic composition but also reside in varying microenvironments and interact with different cell types. Until now, no technology has been fully proven for effective detecting of invasive cancer, which infiltrating the extracellular matrix.

Exploring the ultrafast dynamics of a diarylethene derivative using sub-10 fs laser pulses.

A diarylethene derivative, 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene (DMP), is a photoswitch molecule utilizing a reversible aromatic ring-opening reaction. The quantum yield of the ring-opening reaction is however remarkably low. We investigate the origin of this behaviour by means of ultrafast transient absorption spectroscopy utilizing sub-10 fs pulses, which is an invaluable tool for simultaneously studying both the electronic and the vibrational molecular dynamics.

Distribution of phthalocyanines and Raman reporters in human cancerous and noncancerous breast tissue as studied by Raman imaging.

There is a considerable interest in the developing new diagnostic techniques allowing noninvasive tracking of the progress of therapies used to treat a cancer. Raman imaging of distribution of phthalocyanine photosensitizers may open new possibilities of Photodynamic Therapy (PDT) to treat a wide range of neoplastic lesions with improved effectiveness of treatment through precise identification of malignant areas. We have employed Raman imaging and Raman spectroscopy to analyze human breast cancer tissue that interacts with photosensitizers used in the photodynamic therapy of cancer.

Ultrafast dynamics of metal complexes of tetrasulphonated phthalocyanines.

A promising material in medicine, electronics, optoelectronics, electrochemistry, catalysis, and photophysics, tetrasulphonated aluminum phthalocyanine (AlPcS(4)), is investigated by means of steady-state and time-resolved pump-probe spectroscopies. Absorption and steady-state fluorescence spectroscopy indicate that AlPcS(4) is essentially monomeric. Spectrally resolved pump-probe data are recorded on time scales ranging from femtoseconds to nanoseconds.