Rotational Dynamics In Molecular Solids

Author : Ieva Liepuoniute
Publisher :
ISBN 13 :
Total Pages : 229 pages
Book Rating : 4.:/5 (129 download)

DOWNLOAD NOW!

Download or read book Computational and Experimental Studies of Correlated Dynamics in Molecular Gears, and Crystalline Polarized Rotors in Pillared-Paddlewheel Metal-Organic Frameworks written by Ieva Liepuoniute and published by . This book was released on 2021 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation features a compilation of work that utilized experimental and computational tools to explore the energetics, rotational dynamics and emergent materials properties of solid-state molecular machines. Nanoscale mechanical devices such as molecular gyroscopes and gears can be built using static, lattice forming elements linked to mobile molecular components that make up a hybrid phase called amphidynamic crystals. An underexplored strategy in the development of amphidynamic crystals is to install functional handles on their dynamic components. Collective orientation of such functionalized molecules may lead to tunable thermal, dielectric, and optical properties in response to external physical or chemical influences. Among the most challenging aspects of developing nanoscale solid-state machines is understanding the synergy between structural properties of amphidynamic components, and their individual and collective function and dynamics. Therefore, expanding the number of structural solutions available and the dynamic range that they cover is of current interest. The work presented herein highlights the importance of experimental and computational collaboration in the design of amphidynamic materials, as well as the understanding and tuning of their dynamic properties. Computations played a key role in modeling rotational dynamics outside the experimental time window, characterizing complex motion, mapping out steric and electrostatic interactions between the rotor and their local environment or assisting in new suitable rotator candidate selection. Various computational methods are employed in this dissertation. Density functional theory (DFT) is used to characterize ground state and transition state geometries, establish potential energy surfaces, and unravel rotator-stator interactions. Classical Molecular Dynamics, Metadynamics and Monte Carlo simulations are employed to predict and explain the complex gearing dynamics, study dynamic trajectories, construct potential mean force surfaces, and estimate order-disorder phase transitions. Chapter One is a review article on correlated dynamics in crystalline molecular machines. This chapter describes the state-of-the art of this field and the intellectual framework that may lead to future work. Current molecular and crystal engineering strategies, challenges associated with engineering correlated motion in crystals, and experimental and theoretical tools to explore gearing dynamics are discussed. Chapter Two describes computational studies of tunable rotational dynamics in dirhodium supramolecular gears, highlighting the value of computational methods beyond the limits of the narrow experimental window. In this chapter we used molecular dynamics simulations to probe the gearing mechanism, and calculated the activation barriers to gearing using density functional theory. This work expands the understanding of the key factors determining geared dynamics in the dirhodium supramolecular system and showcases an exciting strategy to tune triptycene gearing to different dynamic regimes via axial ligand exchange. Chapter Three discusses the experimental and computational studies of a new macrocyclic molecular spur gear with enhanced gearing dynamics. Efficient triptycene gear meshing and enhanced concerted dynamics in molecular spur gears require precise inter-gear distances which was achieved through a triptycene cog macrocyclization strategy. Our computational models provide evidence that this is the first system of its kind that prefers gearing over slippage or independent rotation. Chapter Four focuses on the development and characterization of amphidynamic crystals with reorienting dipoles that can spontaneously adopt internal order with a Currie-Weiss-like behavior and a critical temperature that depends on the strength of their dipolar interactions. This chapter highlights the implementation of structural solutions for amphidynamic crystals with intrinsic rotational barriers that are on the order of magnitude of thermal energies at room temperature. Material polarization measurements, coupled-motion dynamics, ultrafast rotation measurements, and dipole-lattice and dipole-dipole interaction simulations are also discussed. Chapter Five establishes a non-conventional strategy to lower the effective activation energy in a crystalline metal organic framework (MOF) with polar phenylenes based on the destabilization of the ground state. This is an alternative strategy to create crystalline dipolar arrays that help realize materials that are self-ordering and susceptible to field-induced macroscopic polarization. Material synthesis, solid-state dynamics obtained by 2H NMR, and computational results are discussed. Chapter Six describes the use of the solid-state photodecarbonylation to synthesize the bis(cyclotryptamine) alkaloid psychotriadine with neighboring fully-substituted stereocenters, so-called vicinal quaternary stereocenters. This chapter discusses how crystalline substrate conformation influences the success or failure of the photodecarbonylation reaction. Experimental and computational strategies to probe the factors that control the success or failure of the key solid-state photodecarbonylation reaction are described.