Incoherent nonlinear photophysical and photochemical processes based on stepwise two-photon absorption (2PA) processes have been recently used in materials science owing to their unique ...photoresponses beyond one-photon processes and lower power thresholds to induce the processes than those of coherent nonlinear optical processes. Among them, nonlinear photochromic materials have received considerable attention because they exhibit unconventional photoresponses compared with other incoherent nonlinear processes such as low-power-threshold nonlinear photoresponses with unimolecular systems, gated photochemical reactions and oxygen-insensitive nonlinear photoresponses. Nonlinear photochromic materials are important not only for colorimetric materials, but also for emergent materials that can enrich the next-generation society such as dynamic holographic materials, which are promising for three-dimensional displays. In this tutorial review, we introduce low-power-threshold nonlinear photochromic materials using stepwise 2PA processes. First, we explain the fundamental concepts of photochemistry as well as photochromic reactions. We attempt to provide an intuitive understanding of incoherent nonlinear optical processes using these fundamental concepts. Then, we introduce several recent examples and potential applications of nonlinear photochromic materials. This tutorial review is important for understanding the scientific progress related to these fields and provides a simple unified picture of the incoherent nonlinear optical properties of different types of photofunctional materials.
Benzo-annulated chromenes, i.e., naphthopyrans, are well-known photochromic molecules that undergo photochemical ring-opening reactions to form two colored open-ring isomers, the transoid-cis and ...transoid-trans forms, upon light irradiation. Though the transoid-cis form returns thermally to the uncolored closed form, the fading rate of the transoid-trans form is extremely slow because of its higher thermal stability. This slow fading behavior of the transoid-trans form is responsible for the persistence of residual color for several minutes to hours, and prevents the application of such molecules to fast photoswitching materials. We have found a new simple and versatile strategy to substantially reduce the amount of the undesirable long-lived colored transoid-trans form by introducing an alkoxy group at the 1-position of azino-fused chromenes, i.e., 8H-pyranoquinazolines. The alkoxy group effectively reduces the formation of the transoid-trans form due to C–H···O intramolecular hydrogen bonding in the transoid-cis form. Moreover, the introduction of a condensed aromatic ring at the 3-position was found to be effective to increase the photosensitivity of the ring-opening reaction. This strategy can also be applied for naphthopyran derivatives and is useful for the development of fast photoresponsive photochromic lenses and fast photoswitching applications such as dynamic holographic materials and molecular actuators.
Negative photochromism, in which a thermally stable colored form isomerizes to the transient colorless form by light irradiation and the back reaction occurs thermally, is advantageous in its ...applications for photoswitching materials because visible light can cause the photochromic color change of the materials. Moreover, the photochromic color change can be induced even on the inside of the materials due to the absence of the reabsorption of the visible excitation light by the photogenerated colorless species. While several negative photochromic compounds have been reported, the time scales of the back reaction are still slower than minutes, and no available fast responsive negative photochromic compounds have been reported. Here, we developed a negative photochromic 1,1′-binaphthyl-bridged phenoxyl–imidazolyl radical complex (BN-PIC) which enables fast photoswitching by visible light. The stable colored BN-PIC shows instantaneous decoloration by visible light irradiation, and the photogenerated colorless form thermally reverts to the initial colored form with a half-life of 1.9 s at room temperature. BN-PIC can also cause the drastic change in the chiroptical properties by the photochromic reaction, and the rate of the thermal back reaction is affected by the chirality of the solvent. Since the negative photochromic reaction can occur on the inside of the materials, the fast negative photochromism is expected to have an impact in the fields of photoresponsive materials of solid states and molecular aggregates.
Biradicaloids in π-conjugated organic molecules have been extensively studied in recent years because of the fundamental insights into the chemical bonds and unique optical, electrical, and magnetic ...properties. Several studies have reported that the spin–spin interactions of biradicaloids with flexible molecular frameworks dynamically evolve correlating with molecular structural changes. Although these dynamic behaviors will provide important insights into the relationship between molecular structures and spin properties, studies on such behaviors have been limited to two-spin systems. Here, we investigated the stepwise photochromic properties of biphotochromic molecules involving multiple spin interactions by double-pulse laser flash photolysis. The one-photon photochromic reaction generates the o-biradical form as the open-closed form, which thermally isomerizes to the o-quinoidal form and reaches the thermal equilibrium state between them. The additional absorption of a photon by the open-closed form leads to the photochromic reaction of the other photochromic unit, resulting in the generation of unpaired spins at the p-position of the central aromatic bridge of the biradical or quinoidal form. Under the situation, while the interaction between the unpaired spins and the o-biradical preferentially produces the p-quinoidal form in which the antiferromagnetic interaction at the p-position is dominant, that between the spins and the o-quinoidal form kinetically produces the bis(o-quinoidal) form followed by the thermal isomerization to the thermodynamically stable p-quinoidal form. These dynamic spin–spin interactions along with the rearrangement of chemical bonds will give a deeper understanding of the singlet biradicaloids and that to bridge organic multiradicals in molecular systems to cooperative spin behaviors in bulk materials.
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•Stepwise two-photon absorption processes involving photochromic reactions are summarized from the viewpoints of history, fundamentals, and applications.•The applications of T-type ...photochromic reactions to stepwise two-photon absorption are efficient strategies to reduce the power threshold of the stepwise two-photon absorption processes.•T-type photochromic compounds whose half-lives of the thermal back reactions are milliseconds to seconds are good candidates for efficient stepwise two-photon photochromic reactions.
Stepwise two-photon absorption (2PA) is one of the nonlinear photoresponses where two photons are sequentially absorbed to proceed a photophysical or photochemical reaction. The stepwise 2PA can selectively produce a higher excited state with relatively high spatial selectivity, and therefore, it can be an efficient tool to explore and realize nonlinear photoresponsive materials beyond Kasha’s rule. Moreover, if a photogenerated chemical species is used as an intermediate state of the stepwise 2PA, the power threshold to promote the stepwise 2PA can be greatly reduced compared with that of a simultaneous 2PA, and conventional LEDs and even sunlight could be used to induce the stepwise 2PA. Because of these advantages, the stepwise 2PA has been widely studied more than a half century ago not only for fundamental physics and chemistry but also for applications to optical memory, holography, and artificial photosynthesis. In this review, we overview various types of stepwise 2PA processes from the viewpoints of history, fundamentals, and applications. Especially we focus on the stepwise 2PA processes related to photochromic reactions because the combination of photochromic reactions and stepwise 2PA processes has realized various potentially-applicable nonlinear photoresponsive materials and found several anomalous phenomena beyond the one-photon photophysical and photochemical reactions. The stepwise 2PA processes are mainly divided into two categories involving an electronic excited state or a photogenerated transient species as the intermediates states of the stepwise 2PA. These two types of the stepwise 2PAs are explained respectively, and finally, the summary and outlook are presented.
To examine the trends of epithelial ovarian cancer histologic subtypes in Japan.
A nationwide retrospective registry study was performed between 2002 and 2015 (Japan cohort, n = 48,640). Trends were ...also examined in The Surveillance, Epidemiology, and End Results Program (US cohort, n = 49,936). Time-specific proportional changes of four major histological subtypes (serous, clear cell, endometrioid, and mucinous) were examined.
The Japan cohort had more stage I disease (44.1% versus 24.9%) and less stage IV disease (10.0% versus 23.1%) than the US cohort (P < 0.001). The Japan cohort had more non-serous histology, particularly clear cell carcinoma (26.9% versus 8.4%), than the US cohort (P < 0.001). In the Japan cohort, proportion of clear cell carcinoma increased significantly from 23.4% to 29.1% between 2002 and 2010 (P < 0.001). Among stage I disease, clear cell carcinoma increased significantly in the Japan cohort from 32.9% to 40.3% between 2002 and 2015 (P < 0.001), whereas mucinous carcinoma increased significantly in the US cohort from 15.0% to 24.8% (P = 0.01). In 2015, clear cell carcinoma was most common among women aged <50 years from the Japan cohort (30.2%) versus serous carcinoma in the US cohort (50.8%). In the Japan cohort, the peak age was 75 years for serous, 57 for clear cell, and 45 for endometrioid carcinoma (P < 0.001). Mucinous carcinoma decreased until 43 years and increased again after age 73 years (P < 0.001).
Characteristics of epithelial ovarian cancer in Japan are largely different compared to the US. In Japan, clear cell carcinoma has increased significantly in recent years to account for nearly 30% of epithelial ovarian cancer.
•The trends in four major histological subtypes of epithelial ovarian cancer (EOC) in Japan and the US were examined.•The characteristics of the histological subtypes of EOC in Japan are distinct from those in the US.•The frequency of clear cell carcinoma has increased in Japan, accounting for almost 30% of EOC in recent years.•The frequency of mucinous carcinoma has increased significantly among elderly in both countries.
There has been a growing interest toward the development of advanced photofunctional materials whose photoresponses involve multiple photons and molecules because these materials show the ...photoresponses which cannot be achieved by a one-photon reaction of a single chromophore. These cooperative interactions of multiple photons and molecules are recently termed as the “photosynergetic” effects, and the understanding and utilization of these effects are becoming important research topics. In this Perspective, we overview the recent progress of the fast T-type photochromic molecules involving the stepwise two-photon absorption processes. Although high power pulse lasers were necessary to induce conventional simultaneous and stepwise two-photon absorption processes, the stepwise two-photon absorption process with the fast photochromic compound can be initiated by extremely weak continuous wave (CW) LEDs. The basic concept and future outlook of the fast photochromism involving the stepwise two-photon absorption process will be discussed.
Multiply aryl-substituted pyrrole-based anion-responsive π-electronic molecules were synthesized. The effects of the introduced aryl moieties on solution-state emissive behaviours were examined, ...depending on the solvent polarity and anion binding.
Multiply aryl-substituted pyrrole-based anion-responsive π-electronic molecules were synthesized. The effects of the introduced aryl moieties on solution-state emissive behaviours were examined, depending on the solvent polarity and anion binding.
A 49-year-old woman presented with nephrotic-range proteinuria, microhematuria, and moderate renal dysfunction. Diuretic-resistant refractory ascites associated with nephrotic syndrome were observed. ...Based on the histopathological findings, the patient was diagnosed with proliferative glomerulonephritis with monoclonal immunoglobulin G deposits (PGNMID). Rituximab was administered due to steroid and immunosuppressive drug resistance, and partial remission was achieved after six months. Cell-free and concentrated ascites reinfusion therapy (CART) performed to treat the refractory ascites improved the ascites and anasarca. Rituximab successfully treated the PGNMID, while CART effectively treated the refractory ascites associated with nephrotic syndrome.
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