Fine-tuning of a thermosalient phase transition by solid solutions

Thermosalient crystals are solids that exhibit motion at the macroscale as a consequence of a thermally induced phase transition. They represent an interesting scientific phenomenon and could be useful as actuators for the conversion of thermal energy into motion or mechanical work. The potential utilization of these miniature transducers in real-world devices requires a controllable phase transition (i.e. a predetermined temperature). While it is difficult to control these performances with a single-component molecular crystal, “tunable” properties could be accomplished by solid solutions. To verify this hypothesis, the thermosalient material [Zn(bpy)Br2] (bpy = 2,2′-bipyridine) was selected and its synthesis was performed in the presence of chloride ions. The resulting mixed crystals ([Zn(bpy)Br2xCl2(1−x)]) show that the product undergoes the expected thermosalient phase transition, and the temperature of the onset of the phase transition and the transition enthalpy depend on the Cl/Br ratio

Photoreactive Zn(II) Coordination Compounds : Exploring Biomimetic Mechanical Motion and Photosalient Behavior

Locomotion plays a pivotal role in the survival of most organisms, enabling essential activities such as foraging, predator evasion, and reproduction. In the realm of biomimetics, seedpod explosion and bark peeling, well-established biological mechanisms employed by various plant species for defense and reproduction, offer a fascinating avenue for exploration. In this study, we present six novel photoreactive Zn(II)-based coordination compounds capable of significant mechanical motion, including explosion and a peeling effect under UV light irradiation. These compounds were synthesized using aryl derivatives of 4-vinylpyridines, namely, 4spy (4-styrylpyridine), 3tpy (4-(3-(thiophene-3-yl)vinyl)pyridine), and 2tpy (4-(2-(thiophene-2-yl)vinyl)pyridine), in conjunction with chloride or bromide colinkers. The resulting complexes, [ZnCl2(4spy)2] (1), [ZnCl2(3tpy)2] (2), [ZnCl2(2tpy)2] (3), [ZnBr2(4spy)2] (4), [ZnBr2(3tpy)2] (5), and [ZnBr2(2tpy)2] (6), were characterized as isostructural, with slight variations observed in compound 6’s structural packing. X-ray diffraction analysis confirmed the tetrahedral geometry of Zn(II) in all six complexes. Notably, compounds 1–5 exhibited coordination involving both planar and nonplanar linkers, leading to an expected 50% photoreaction. Interestingly, despite not meeting Schmidt’s criteria, the nonplanar linkers also exhibited photoreaction at slower rates. Furthermore, alongside the UV-induced photoreaction, these compounds displayed intriguing and vigorous mechanical motion reminiscent of a photosalient effect, characterized by rolling, cracking, jumping, and fragmentation. In contrast, compound 6 demonstrated complete photoreaction due to both coordinated linkers adopting planar configurations. Additionally, these crystals exhibited a peeling effect under UV irradiation, akin to the natural peeling of tree bark due to aging. These findings highlight the potential of Zn(II)-based coordination compounds as promising candidates for developing metal-based photoactuators and optical switches, with biomimetic applications

Solid-State [2+2] Photoreaction of Isostructural Cd(II) Metal Complexes and Solid-State Fluorescence

A green method to synthesize cyclobutane derivatives has been developed over the past three decades in the form of solid-state [2+2] photochemical reactions. These solid-state reactions also play a major role in the structural transformation of hybrid materials. In this regard, crystal engineering has played a major role in designing photoreactive molecular systems. Here, we report three novel binuclear Cd(II) complexes with the molecular formula [Cd2(4spy)4L4], where 4spy = 4-styryl pyridine and L = p-toluate (1); 4-fluorobenzoate (2); and 3-fluorobenzoate (3). Although three different benzoates are used, all three complexes are isostructural, as corroborated through SCXRD experiments. Structural analysis also helped in identifying two potential photoreactions. These are both intra- and intermolecular in nature and are driven by the head-to-head (HH) and head-to-tail (HT) alignment of 4spy linkers within these metal complexes. 1H NMR spectroscopy studies showed evidence of a quantitative head-to-head photoreaction in all these three complexes, and SCXRD analysis of the recrystallization of the photoproducts also provided confirmation. TGA studies of these photoreactive complexes showed an increase in the thermal stability of the complexes due to the solid-state photoreaction. Photoluminescence studies of these complexes have been conducted, showing a blue shift in emission spectra across all three cases after the photoreaction

Stepwise Photoreactions and Photosalient Effects in Isostructural Donor-Acceptor Molecular Complexes with Tunable Optical Properties

In the rapidly evolving field of molecular design, donor-acceptor complexes have garnered significant attention due to their unique optical, electronic, and photoreactive properties. This study explores the synthesis of donor-acceptor molecular complexes using electron-deficient tetrafluoroterephthalate and four electron-rich 4-vinylpyridine derivatives. Due to the similar chemical structures of 4-vinylpyridine derivatives (2tpy, 3tpy, 4spy, and 3F-4spy), three of the four complexes exhibit isostructural packing. These compounds display segregated arrangements and undergo [2 + 2] solid-state photoreactions even under ambient light, with stepwise structural evolution captured by single-crystal-to-single-crystal X-ray diffraction. Under UV irradiation, the crystals show single-step photoreactions along with distinct photosalient behavior. The charge-transfer nature of these complexes, which drives their photoreactivity under ambient light, is investigated through optical absorption studies and Raman spectroscopy. The vibrational signatures obtained from Raman experiments are further interpreted using TD-DFT calculations, offering detailed insight into the electronic structure and molecular interactions

In-situ photomechanical bending in a photosalient Zn-based coordination polymer probed by photocrystallography

Photomechanical bending or mechanical flexibility in single crystals is an interesting landscape for innovative technological applications, including smart medical devices, molecular machines, artificial muscles, microrobots, and flexible electronic actuators. However, metal-organic crystals with multiple dynamic effects such as bending (in-situ), jumping, fracturing, and splitting in the absence of mechanical energy or temperature is interesting and relatively unexplored. The development of these materials presents significant challenges, requiring a thorough grasp of the underlying mechanisms for practical applications. Herein, we developed a Zn based 1D coordination polymer (CP) crystal {[Zn(DCTP)(4-nvp)2]·(CH3OH)}n (1) {H2DCTP = 2,5-dichloroterephthalic acid; 4-nvp = 4-(1-naphthylvinyl)pyridine} which undergoes [2 + 2] cycloaddition under both UV irradiation and sunlight to generate a partially dimerized product of a two-dimensional coordination polymer (2D CP) [Zn(DCTP)(rctt-4-pncb)]n (i201). During UV irradiation, these single crystals exhibit photomechanical effects like jumping, bending, cracking, and swelling to relieve anisotropic strain from the light. Surprisingly, bent-shaped single crystals (1b) identical in structure to 1 were also obtained in-situ without any external stimuli, simply by keeping reaction mixture for an extended period. A time-resolved photocrystallographic study fully described the photoinduced structural transformation. Nanoindentation measurements complemented a DFT study of mechanical property trends for irradiated and bent Zn-based photosalient crystals

Overview of business hyper-automation

Business hyper-Automation has emerged as a new topic with the advancement of AI, machine learning, process automation, sensing technology, blockchain, etc. It starts attracting industry interest as well, as many IT giants are establishing the market of business hyper-Automation. By organically combining these technologies, business hyper-Automation promises us flexible service delivery, intelligent business scheduling, resilience to unexpected changes, and significant reduction of workforce need. Around this novel concept, we are to discuss the motivation of business hyper-Automation and typical technologies employed by it. An outlook to related research topics and the future of hyper-Automation is conducted in the end. © 2022 IEEE