Rabih O. Al-Kaysi

King Saud bin Abdulaziz University for Health Sciences | KSAU-HS · College of Science and Health Professions

We reported the synthesis and characterization of a new type of photoisomerizable molecule (Z)-5-(anthracen-9-ylmethylene)-3-butylthiazolidine-2,4-dione (C4-ATD), whose Z/E isomerization induces large geometry changes but only slight changes in its absorption profile. Acicular micro-molecular crystals made from C4-ATD were fabricated using the seed...

In recent years, significant advancements have occurred in the development of smart materials, particularly in creating molecular crystals that can convert light energy into mechanical work. In this study, we focus on the synthesis, characterization, and photomechanical behavior of a new molecule, bis(2,2,2-trifluoroethyl) (E)-2-(3-(anthracen-9-yl)...

In the last century, molecular crystals functioned predominantly as a means for determining the molecular structures via X-ray diffraction, albeit as the century came to a close the response of molecular crystals to electric, magnetic, and light fields revealed that the physical properties of molecular crystals were as rich as the diversity of mole...

The Special Issue on “Photoresponsive Molecular Crystals” is a collection of four original research articles dedicated to theoretical and experimental research works providing new insights and experimental findings in the field of photoresponsive crystals [...]

Photomechanical molecular crystals have garnered attention for their ability to transform light into mechanical work, but difficulties in characterizing the structural changes and mechanical responses experimentally have hindered the development of practical organic crystal engines. This study proposes a new computational framework for predicting t...

9-Methylanthracene (9MA) undergoes a concerted [4 + 4] photodimerization in its crystal form that can be harnessed in order to generate photomechanical motions such as bending, twisting, and expansion. As described in this paper, 9MA nanowires were grown in anodic aluminum oxide (AAO) templates with the goal of using the crystal expansion to genera...

In this short note we describe the photochemical synthesis of (2E,4Z)-5-(anthracen-9-yl)-2-cyanopenta-2,4-dienamide (4) from the corresponding (2E,4E)-5-(anthracen-9-yl)-2-cyanopenta-2,4-dienamide (3) and subsequent purification by precipitation from aqueous surfactant. Compound like 4 belongs to a family of anthracene derivatives capable of formin...

Hollow organic molecular cocrystals comprised of 9‐methylanthracene‐1,2,4,5‐tetracyanobenzene (9MA‐TCNB) and naphthalene‐1,2,4,5‐tetracyanobenzene (NAPH‐TCNB) were fabricated using a surfactant‐mediated co‐reprecipitation method. The crystals exhibit a narrow size distribution that can be easily tuned by varying the concentration of surfactant and...

Crystals composed of photoreactive molecules represent a new class of photomechanical materials with the potential to generate large forces on fast timescales. An example is the photodimerization of 9-tert-butyl-anthracene ester (9TBAE) in molecular crystal nanorods that leads to an average elongation of 8%. Previous work showed that this expansion...

9-anthracene carboxylic acid derivatives comprise a family of thermally reversible photomechanical molecular crystals. The photomechanical response relies on a [4+4] photodimerization followed by dissociation that occurs on timescales of seconds...

The preparation of organic crystal microwires that transform light into oscillatory motion is reported by Rabih O. Al‐Kaysi, Christopher J. Bardeen et al. in their Research Article (DOI: 10.1002/anie.202012417). A diolefinanthracene derivative undergoes E–Z photoisomerization to generate molecular‐scale motion. When microwires composed of this mole...

Organische Kristall‐Mikrodrähte, die Licht in oszillatorische Bewegung umwandeln, werden im Forschungsartikel von Rabih O. Al‐Kaysi, Christopher J. Bardeen et al. vorgestellt (DOI: 10.1002/ange.202012417). Ein Diolefinanthracen‐Derivat durchläuft eine E‐Z‐Photoisomerisierung, um Bewegung auf molekularer Ebene zu erzeugen. Wenn Mikrodrähte aus diese...

The ability to exhibit life‐like oscillatory motion fueled by light represents a new capability for stimuli‐responsive materials. Although this capability has been demonstrated in soft materials like polymers, it has never been observed in molecular crystals, which are not generally regarded as dynamic objects. In this work, it is shown that molecu...

When exposed to a combination of ultraviolet and visible light, crystalline microwires composed of (Z)‐2‐(3‐(anthracen‐9‐yl)allylidene)malononitrile ((Z)‐DVAM) undergo oscillating deformations that mimic the motion of biological flagella and move the crystals through water. This life‐like mechanical motion is fueled by reversible E→Z photoisomeriza...

Hollow organic molecular cocrystals comprised of 9-methylanthracene-1,2,4,5-tetracyanobenzene (9MA-TCNB) and naphthalene-1,2,4,5-tetracyanobenzene (NAPH-TCNB) were fabricated using a surfactant-mediated co-reprecipitation method. The crystals exhibit a narrow size distribution that can be easily tuned by varying the concentration of surfactant and...

A naphthalene‐1,2,4,5‐tetracyanobenzene cocrystal with two symmetrical closed cavities can be grown using surfactant‐mediated coprecipitation combined with gentle agitation. During growth, the molecular crystal microcapsule can be filled with a fluorescent dye that remains contained for hours. The images show a single dye‐filled organic cocrystal v...

4-fluoro-9-anthracenecarboxylic acid (4F-9AC) is a thermally reversible (T-type) photomechanical molecular crystal. The photomechanical response is driven by a [4+4] photodimerization reaction, while the photodimer dissociation determines the reset time. In this paper, both the chemical kinetics of dimer dissociation (using a microscopic fluorescen...

(E)-4-fluoro-cinnamaldehyde malononitrile ((E)-4FCM) is a new phenylbutadiene derivative that undergoes a [2+2] photocycloaddition in the crystal form. Optical absorption and proton nuclear magnetic resonance (1HNMR) measurements demonstrate that the solid-state (E)-4FCM photodimerization is a negative photochromic reaction that proceeds to nearly...

Some anthracene derivatives can transform photons into molecular‐scale motions by undergoing photochemical reactions. Grown into nano‐ or microcrystals, these derivatives can amplify molecular‐scale motions to produce actuation on much larger length scales. In this chapter, we describe the basic principles of photomechanical materials based on mole...

The molecule (E)‐(5‐(3‐anthracen‐9‐yl‐allylidene)‐2,2‐dimethyl‐[1,3] dioxane‐4,6‐dione) (E‐AYAD) undergoes E→Z photoisomerization. In the solid state, this photoisomerization process can initiate a physical transformation of the crystal that is accompanied by a large volume expansion (ca. 10 times), loss of crystallinity, and growth of large pores....

Tanz der Moleküle: Das Molekül (E)‐(5‐(3‐Anthracen‐9‐yl‐allyliden)‐2,2‐dimethyl‐[1,3]‐dioxan‐4,6‐dion) durchläuft eine E→Z‐Photoisomerisierung im kristallinen Zustand, einhergehend mit Volumenexpansion, Verlust der Kristallinität und der Ausbildung hoher Porosität. Dieser Kristall‐Gel‐Übergang kann genutzt werden, um superparamagnetische Nanopartik...

Block-like microcrystals composed of cis-dimethyl-2(3-(anthracen-9-yl)allylidene)malonate are grown from aqueous surfactant solutions. A pulse of 405 nm light converts a fraction of molecules to the trans isomer, creating an amorphous mixed...

When photochromic molecules are organized in a crystal, the small-scale forces generated by molecular photoisomeriza-tion events can add together to generate work on micro- or macroscopic length-scales. In this work, photomechanical nanocrystals themselves are organized on macroscopic length-scales using a porous inorganic template. The organic dia...

Fluorescent switches based on spirocyclic zwitterionic Meisenheimer (SZMC) complexes are stimuli-responsive organic molecules with application in a variety of areas. To expand their functionality, novel switching mechanisms are herein reported for these systems: (a) acid- and redox-triggered formation of an additional protonation state with distinc...

A surfactant-assisted seeded-growth method is used to form single crystal platelets composed of 9-Methylanthracene with two different internal molecular orientations. The more stable form exhibits a photoinduced twisting, as observed previously for 9-Methylanthracene microribbons grown by the floating drop method. However, the newly discovered elon...

Molecules and materials showing stimulus-induced modulation of their optical properties are of interest in a large variety of areas. In this paper, we focus on fluorescent switches based on stable spirocyclic zwitterionic Meisenheimer compounds (SZMC), which are composed of a 2,4,6-trisubstituted cyclohexadienyl anion chromophore fused with a triaz...

A surfactant‐assisted seeded‐growth method is used to form single crystal platelets composed of 9‐Methylanthracene with two different internal molecular orientations. The more stable form exhibits a photoinduced twisting, as observed previously for 9‐Methylanthracene microribbons grown by the floating drop method. However, the newly discovered elon...

Dimethyl-2(3-anthracen-9-yl)allylidene)malonate (DMAAM) is a divinylanthracene derivative that photoisomerizes between its (E) and (Z) conformations. Crystalline nanowires composed of this molecule undergo a rapid coiling motion when exposed to visible light. In this paper, a variety of experimental techniques are used to investigate the mechanism...

Stable zwitterionic spirocyclic Meisenheimer compounds were synthesized using a one-step reaction between picric acid and diisopropyl (ZW1) or dicyclohexyl (ZW3) carbodiimide. A solution of these compounds displays intense orange fluorescence upon UV or visible light excitation, which can be quenched or “turned-off” by adding a mole equivalent amou...

Photomechanical materials require a molecular photochemical element that changes light energy into mechanical motion. This chapter focuses on molecular crystal systems in which photochemical changes generate mechanical motion on length scales greater than the molecular dimensions. Next, it reviews the different modes by which photoreactive crystals...

When a suspension of the tert-butyl ester of 4-fluoroanthracene-9-carboxylic acid (4F9AC) was slowly hydrolyzed, highly branched photomechanical microcrystals of 4F9AC were grown. Exposure to UV light caused the branches to undergo a reversible sweeping motion that could be used to move and concentrate silica microspheres on a surface.

The photodimerization of 9-tert-butyl-anthracene ester in molecular crystal nanorods can cause expansions of up to 15%. This expansion results from the formation of a metastable crystalline intermediate, the solid-state reacted dimer (SSRD). In this paper, a combination of powder X-ray diffraction, solid-state nuclear magnetic resonance, and comput...

Anthracene derivatives with a 1,3-butadiene group attached at the 9-position can undergo E ↔ Z (trans ↔ cis) photoisomerization reactions, providing a route to new photomechanical materials. In this paper, we report the properties of a new anthracene derivative, 2-(3-anthracen-9-yl-allylidene)-malononitrile (9DVAM). The structure, photophysics and...

Photomechanical molecular crystals can undergo a variety of light-induced motions, including expansion, bending, twisting, and jumping. The use of more complex crystal shapes may provide ways to turn these motions into useful work. To generate such shapes, pH-driven reprecipitation has been used to grow branched microcrystals of the anthracene deri...

Photomechanical molecular crystals can undergo a variety of light-induced motions, including expansion, bending, twisting, and jumping. The use of more complex crystal shapes may provide ways to turn these motions into useful work. To generate such shapes, pH-driven reprecipita-tion has been used to grow branched microcrystals of the anthracene der...

An alternative and improved method for the synthesis of 1,8-difluoroanthracene 5 is described. The precursor 1,8-difluoro-9,10-anthraquinone 4 was synthesized by precipitating the water-soluble 1,8-diazonium-9,10-anthraquinone fluoroborate 3 using isopropanol, before thermally decomposing it via the Balz-Schiemann reaction to yield 4 in the form of...

Simple, fast, large-scale, and cost-effective preparation of uniform controlled magnetic nanoparticles remains a major hurdle on the way towards magnetically targeted applications at realistic technical conditions. Herein, we present a unique one-pot approach that relies on simple basic hydrolytic in situ coprecipitation of inexpensive metal salts...

(E)-3-(anthracen-9-yl)acrylic acid (9-AYAA) exhibits a strong photomechanical response in bulk crystals but is challenging to grow in microcrystalline form. High quality microcrystals of this molecule could not be grown using techniques like sublimation, reprecipitation, and the floating drop method. If the tertbutyl ester of 9-AYAA is used as a st...

Four fluorinated derivatives of 9-anthracene carboxylic acid (9AC), a molecule that shows a reversible photomechanical response in its crystal form, have been synthesized and characterized. The spectroscopic properties and crystal structures of 4-fluoro-9-anthracene carboxylic acid (4F-9AC), 2-fluoro-9-anthracene carboxylic acid (2F-9AC), 10-fluoro...

9-tert-Butylanthracene undergoes a photochemical reaction to form its strained Dewar isomer, which thermally back-reacts to reform the original molecule. When 9-tert-butylanthracene is dissolved in a polymer host, we find that both the forward and reverse isomerization rates are pressure-dependent. The forward photoreaction rate, which reflects the...

Organic molecules can transform photons into Angstrom-scale motions by undergoing photochemical reactions. Ordered media, for example, liquid crystals or molecular crystals, can align these molecular-scale motions to produce motion on much larger (micron to millimeter) length scales. In this Review, we describe the basic principles that underlie or...

Single crystal nanowire, microrods and Micro-multipods made from (Z)-dimethyl 2-(3-(anthracen-9-yl)allylidene)malonate 5, or (E)-dimethyl 2-(3-(anthracen-9-yl)allylidene)malonate 4, were fabricated using Anodic Aluminium Oxide (AAO) templates. Nanowires of 5, with an average diameter of 230 nm or 100 nm and a length of 55 m, were suspended in an a...

Molecular crystal nanowires composed of an anthracene-9-(1,3-butadiene) derivative exhibit a rapid transition from straight to highly coiled structures when exposed to a pulse of visible light. The curling does not depend on the direction of light illumination and occurs for nanowires composed of either the E or Z isomer. The shape change is driven...

We have fabricated surface-modified paclitaxel nanowires (SM-PNs) with a precise diameter and an average length of 50 μm. The surface of these nanowires is coated with a monolayer of octadecylsiloxane (ODS), which prevents aggregation and enhances dispersivity in aqueous media. This system constitutes a novel drug delivery vehicle based on one-dime...

In the first part of this work, we present an experimental study of the precipitation/redissolution reaction-diffusion system of initially separated components in two distinct organic gels: agar and gelatin. The system is prepared by diffusing a concentrated ammonia solution into a gel matrix that contains nickel sulfate. In agar, the system exhibi...

Given the rapid advances in the fabrication of nanostructures composed of inorganic materials, scientists have in recent years sought new methods for the fabrication of nanostructures composed of organic molecules. Organic nanostructures are promising for applications ranging from drug delivery to photomechanical actuation. This chapter will survey...

Molecular crystals composed of 9-anthracene carboxylic acid (9AC) can undergo reversible light-induced mechanical motions driven by a [4 + 4] photodimerization reaction. This paper explores the structure, photophysics, and photomechanical response of a family of anthracene carboxylic acid derivatives, with the goal of finding materials that have co...

9-Anthracenecarboxylic acid, a molecule that undergoes a reversible [4 + 4] photodimerization, is prepared in the form of oriented crystalline microribbons. When exposed to spatially uniform light irradiation, these photoreactive ribbons rapidly twist. After the light is turned off, they relax back to their original shape over the course of minutes...

Nanowires composed of the anti-cancer drug Paclitaxel (Taxol) were fabricated using solvent annealing method inside Anodic Aluminum Oxide (AAO) templates. Surface modification of the AAO template with n-octadecyltrichlorsilane (OTS), prior to loading with Taxol, prevented the nanowires from agglomerating after dissolving the template in 20% phospho...

A series of 9-anthroateesters that can form photoresponsive molecular crystal nanorods is prepared and their properties are investigated. All crystal structures that can support a [4 + 4] photodimerization reaction lead to nanorods that undergo photomechanical deformations without fragmentation. In order to determine the molecular-level motions tha...

Reaction of gaseous HCl with Eosin-Y disodium salt (Eosin-Y center dot 2Na) nanorods nested inside anodic aluminum oxide templates (AAO), produced perforated Eosin-Y free acid (Eosin-Y-FA) nanorods with surface nanoholes on the order of 50 nm in diameter. Diffusion of different acids yielded different surface patterns with retention of the overall...

The reaction of single-component molecular crystal nanorods with a second species to form cocrystal nanorods is described. Single-component crystalline nanorods, composed of 9-methylanthracene (9-MA), are grown in a porous anodic aluminum oxide template. These templated rods are then exposed to a suspension of 1,2,4,5-tetracyanobenzene (TCNB) in wa...

The impact of different preparation conditions and post-deposition annealing treatments on pristine poly(3-hexyl-thiophene) (P3HT) thin-film photovoltaic devices are investigated with respect to device parameters, surface roughness, and exciton dynamics. Devices were realized from the slow evaporating solvent orthodicholorobenzene (ODCB) and the fa...

Organic nanostructures are new comers to the fields of nanoscience and nanotechnology. In recent years novel methods for controlling the growth and uniformity of one-dimensional (1D) organic nanostructures (nanowires and nanotubes) have been developing. The use of hard templates as molds for the formation of organic nanowires or nanotubes seems to...

We report a method for the preparation of silica-coated molecular crystal nanorods. A sol-gel method was used to make silica nanotubes inside anodized alumina templates. The nanotubes were then loaded with 9-anthracene carboxylic acid (9-AC) and solvent annealed to produce silica-coated organic nanorods. The core-shell structure was confirmed using...

The spectroscopy of solid anthracene is examined both experimentally and theoretically. To avoid experimental complications such as self-absorption and polariton effects, ultrathin polycrystalline films deposited on transparent substrates are studied. To separate the contributions from different emitting species, the emission is resolved in both ti...

Meisenheimer complexes are important intermediates in Nucleophilic Aromatic Substitution Reactions (S(N)Ar). They are formed by the addition of electron rich species to polynitro aromatic compounds or aromatic compounds with strong electron withdrawing groups. It is possible to distinguish two types of Meisenheimer or sigma-complexes, the sigma(H)-...

The dianthracene molecule 9-anthracenecarboxylic acid, methylene ester (9AC-ME) was synthesized and used to form molecular crystal nanorods using anodized aluminum oxide templates. A high-temperature solvent annealing process generated a crystal polymorph where neighboring monomers had overlapping anthracene moieties. Subsequent exposure to ultravi...

The development and characterization of a quartz crystal microbalance (QCM) sensor for the direct detection of aerosolized influenza A virions is reported. Self-assembled monolayers (SAMs) of mercaptoundecanoic acid (MUA) are formed on QCM gold electrodes to provide a surface amenable for the immobilization of anti-influenza A antibodies using NHS/...

A new method is presented for analyzing the effects of self-absorption on photoluminescence integrating sphere quantum yield measurements. Both the observed quantum yield and luminescence spectrum are used to determine the self-absorption probability, taking into account both the initial emission and subsequent absorption and reemission processes....

The use of an intermolecular photochemical reaction to achieve large physical displacements in a different type of structure such as organic molecular crystal nanorods is discussed. The photo-chemical changes drive a reconstructive crystal-to-crystal phase transition that leads to crystal fragmentation and disintegration. The high surface-to-volume...

In this work we investigate a new fluorescent molecular switch based on the interconversion between the fluorescent zwitterionic form (ZW1) and the non-fluorescent anionic state (MC2) of a spirocyclic Meisenheimer complex of 1,3,5-trinitrobenzene. Density functional theory molecular orbital calculations reveal that photo-induced electron transfer f...

Nanorods composed of 9-tert-butylanthroate (9-TBAE) are synthesized using an Al2O3 template and solvent annealing. The rods consist of micron-scale crystalline domains, and UV light induces a [4 + 4] photodimerization that results in a uniform 15% expansion along the rod axis. This is in contrast to random 9-TBAE crystals, which disintegrate under...

We examine the photophysics of a series of molecules consisting of a benzthiadiazole core surrounded by a network of benzyl ether arms terminated by aminopyrene chromophores, which function as both energy and electron donors. Three classes of molecules are studied: dendrimers whose peripheries are fully decorated with aminopyrene donors (F), disubs...

The absorption, fluorescence, and photostability of five conjugated chromophores: perylene, 2,5,8,11-tetra-t-butyl perylene (TTBP), perylene orange (PO), perylene red (PR), and a zwitterionic Meisenheimer complex (MHC), are studied as a function of concentration in poly(methyl methacrylate) (PMMA). At 1 mM concentrations, all five molecules exhibit...

Al(2)O(3) filters (200 nm) are used as templates to form polymer nanotubes containing an energy donor (perylene). The perylene is isolated from chemical interactions but can undergo electronic energy transfer to acceptor molecules in aqueous solutions passing through the membrane. This energy transfer is analyzed quantitatively in terms of both rad...

[reaction: see text] We have designed and synthesized difunctionalized dendrimers containing two donors in the periphery and an acceptor at the core to serve as scaffolds for comparison with linear analogues to investigate the advantage of dendritic scaffolds for energy and charge transfer. Comparison of these dendrimers with the fully decorated de...

Nanorods composed of a variety of conjugated organic molecules were synthesized using an anodized alumina template and solvent annealing; detailed study of 200 nm thick 2,7-di-t-butylpyrene rods showed they are crystalline, with single domains extending over several microns.

Nanoparticles of a novel organic zwitterionic Meisenheimer complex, N',N' ',N' ''-tri(isopropyl)-4-oxo-6-(isopropyliminio)-2-s-(2H)triazinespiro-1'-2',4',6'-trinitrocyclohexadienylide, were synthesized by reprecipitation in water under different conditions. While reprecipitation alone resulted in a suspension of amorphous particles that fell out of...

Photooxidation of 1,1,2,2-tetra-tert-butyl-1,2-diphenyldisilane, 1, by triplet sensitizers in CHCl3/CCl4 solutions yields chlorosilane, 2, in high chemical yield. The quantum yield for formation of 2 depends on the energy of the ion radical pair formed following initial electron transfer. Dissociative return electron transfer (DRET) is proposed as...

Reaction of picric acid with diisopropylcarbodiimide produces a pale yellow 1:1 adduct N-(2,4,6-trinitrophenyl)-N,N-di(isopropyl)urea (5) and a 1:2 adduct fluorescent red zwitterionic Meisenheimer complex (6) as approximately N,N,N-tri(isopropyl)-4-oxo-6-(isopropyliminio)-2-s-(2H)triazinespiro-1-2,4,6-trinitro cyclohexadienylide. Crystals of (5) ar...

In this communication we present the first stable zwitterionic spirocyclic Meisenheimer compound based on an N --> N rearrangement in the reaction between picric acid and diisopropylcarbodiimide. The structure was confirmed by single-crystal X-ray diffraction. Furthermore, this compound exhibits interesting fluorescence properties (phi(f) = 0.4-0.5...

Quaternary ammonium persulfates as free-radical initiators for high-temperature polymerization are synthesized and their shelf-life stability investigated. These initiators do not have gaseous byproducts and are therefore ideal for frontal polymerization, a process in which polymeric materials are produced via a thermal front that propagates throug...