Development Of Theoretical Chemistry Research Articles

Noncovalent Interactions in Organometallic Chemistry: From Cohesion to Reactivity, a New Chapter.

Noncovalent interactions (NCIs) have long interested a vast community of chemists who investigated their "canonical categories" derived from descriptive crystallography, e.g., H-bonds, π-π interactions, halogen/chalcogen/tetrel bonds, cation-π and C-H-π interactions, metallophilic interactions in the broad sense, etc. Recent developments in theoretical chemistry have enabled the treatment of noncovalent interactions under new auspices: dispersion-force-inclusive density functionals have emerged, which are reliable for modeling small to large molecular systems. It is possible to perform the full analysis of the contributions of London, Debye, and Keesom forces, i.e., the main components of van der Waals forces, by the DFT-D and ab initio methods at a reasonable computational cost. Our research has been focusing for now 15 years on the role of NCIs in the cohesion of organometallic complexes. NCIs are not only effective in Werner's secondary coordination sphere but also in the metal's primary one. The stabilization of electron-unsaturated transition metal complexes by hemichelation, metal-metal donor-acceptor complexes, and self-aggregation of cationic Rh(I) chromophores have indeed outlined the significance of the London dispersion force as an attractive force operating throughout the whole molecule or molecular assembly. The recent outburst of interest in C-H bond functionalization led us to address the broader question of reaction and catalyst engineering: although one can now satisfactorily analyze bonding and molecular cohesion in transition-metal-based organometallic systems, can modern theoretical methods guide reactivity exploration and the engineering of novel catalytic systems? We addressed this question by investigating the ambiphilic metal-ligand activation/concerted metalation-deprotonation mechanism involved in transition-metal-catalyzed directed C-H bond functionalization. This endeavor was initiated having in scope the construction of a rationale for the transposition of 4-5d metal chemistry to earth-abundant 3d metals. In this base-assisted mechanism of C-H bond metalation, agostic interactions are necessary but not sufficient because C-H bond breaking actually relies on the attractive NCI coding of a proton-transfer step and the minimization of metal-H repulsion. This Account introduces the recent shift of our research toward the construction of an NCI-inclusive paradigm of chemical reactivity engineering based on experimental efforts propped up by state-of-the-art theoretical tools.

Attochemistry: Is Controlling Electrons the Future of Photochemistry?

Controlling matter with light has always been a great challenge, leading to the ever-expanding field of photochemistry. In addition, since the first generation of light pulses of attosecond (1 as = 10-18 s) duration, a great deal of effort has been devoted to observing and controlling electrons on their intrinsic time scale. Because of their short duration, attosecond pulses have a large spectral bandwidth populating several electronically excited states in a coherent manner, i.e., an electronic wavepacket. Because of interference, such a wavepacket has a new electronic distribution implying a potentially different and totally new reactivity as compared to traditional photochemistry, leading to the novel concept of "attochemistry". This nascent field requires the support of theory right from the start. In this Perspective, we discuss the opportunities offered by attochemistry, the related challenges, and the current and future state-of-the-art developments in theoretical chemistry needed to model it accurately.

Quantifications and Applications of Relative Fisher Information in Density Functional Theory.

Though density functional theory is widely accepted as one of the most successful developments in theoretical chemistry in the past few decades, the knowledge of how to apply this new electronic structure theory, to help us better understand chemical processes and transformations, is still an unaccomplished task. The information-theoretic approach is emerging as a viable option for that purpose in the recent literature, providing new insights about steric effect, cooperativity, electrophilicity, nucleophilicity, stereoselectivity, homochirality, etc. In this work, based on the result from a recent paper by one of us [ J. Chem. Phys, 2019, 151, 141103], we present two quantifications of the relative Fisher information and discuss their physiochemical properties and possible applications. To that end, their analytical properties have been elucidated. They have also been applied to six categories of systems to illustrate their applicability. A better descriptor to quantify the single bond rotation barrier has been obtained. The relative Fisher information can also simultaneously determine electrophilicity and nucleophilicity, and effectively describe helical structures with different homochiral and heterochiral propensities. As integral parts of the information-theoretic approach, these newly introduced quantities will provide us with more analytical tools toward the long-term goal of crafting a chemical reactivity theory in the density-based language.

Combined Theoretical and Experimental Studies of Sodium Battery Materials.

Owing to developments in theoretical chemistry and computer power, the combination of calculations and experiments is now standard practice in understanding and developing new materials for battery systems. Here, we briefly review our recent combined studies based on density functional theory and molecular dynamics calculations for electrode and electrolyte materials for sodium-ion batteries. These findings represent case studies of successful combinations of experimental and theoretical methods.

Developments in Theoretical Chemistry

Developments in Theoretical Chemistry

Developments in Theoretical Chemistry.

Developments in Theoretical Chemistry.

Normed repeat space and its super spaces: fundamental notions for the second generation Fukui project

Fukui’s DNA problem is a long-range target of the international and interdisciplinary joint project initiated by Kenichi Fukui in 1992, whose underlying motive has been to cultivate a new interdisciplinary region between chemistry and mathematics for a future development of theoretical chemistry. “Can the conductivity and other properties of a single-walled carbon nanotube be analyzed in the setting of a *-algebra equipped with a complete metric?” This metric problem is fundamental to proceed towards a solution of Fukui’s DNA problem. To affirmatively solve this metric problem, we establish, here in this paper, the new notion of normed repeat space $${\fancyscript{X}_{r}(q, d, p)}$$ . The normed repeat space $${\fancyscript{X}_{r}(q, d, p)}$$ is an intermediate theoretical device to shift from periodic polymers to aperiodic polymers like DNA and RNA in the above-mentioned Fukui Project. The space $${\fancyscript{X}_{r}(q, d, p)}$$ is a Banach algebra for all 1 ≤ p ≤ ∞, and $${\fancyscript{X}_{r}(q, d, p)}$$ forms a C*-algebra for p = 2. Here, polymer moiety size number q and dimension number d are arbitrarily given positive integers. The generalized repeat space $${\fancyscript{X}_{r}(q, d)}$$ is included in the normed repeat space $${\fancyscript{X}_{r}(q, d, p)}$$ , which in turn is included in one of its super spaces $${\fancyscript{X}_{B}(q, d, p)}$$ so that aperiodic polymers can be represented and investigated in the setting of this super space $${\fancyscript{X}_{B}(q, d, p)}$$ .

Some key historical highlights in the evolution of the modern concept of valence

The closely related concepts of valence and chemical bonding have played a pivotal role in the development of theoretical chemistry, and are now viewed as two of the most important concepts in the entire history of chemistry. The occasion of the fortieth anniversary of the appearance of C.A. Coulson's book Valence affords a convenient opportunity to survey some of the major developments in the evolution of the concept of valence, and to place the pioneering contributions of Coulson in an appropriate historical setting. Our review starts from the earliest speculations on the subject by ancient Greek philosophers, traces the evolution of the concept down to modern times, and ends up by examining possible ways in which our ideas on valence could mature over the next forty years.

Time, Structure, and Fluctuations

Fundamental conceptual problems that arise from the macroscopic and microscopic aspects of the second law of thermodynamics are considered. It is shown that nonequilibrium may become a source of order and that irreversible processes may lead to a new type of dynamic states of matter called "dissipative structures." The thermodynamic theory of such structures is outlined. A microscopic definition of irreversible processes is given, and a transformation theory is developed that allows one to introduce nonunitary equations of motion that explicitly display irreversibility and approach to thermodynamic equilibrium. The work of the group at the University of Brussels in these fields is briefly reviewed. In this new development of theoretical chemistry and physics, it is likely that thermodynamic concepts will play an ever-increasing role.

Humanism in Chemistry

THE academic scientist of the fifteenth and early sixteenth cen turies has often appeared to historians to be a reactionary, pedantically pursuing the literal words of ancient authors at the expense of the fertile ideas of his immediate predecessors. Yet time and again the most stimulating scientists clothed their ideas in the language of humanism and, indeed, seem to have derived them from the same fount at which the pedants worshiped. We are so familiar with the fact that Copernicus felt himself to be only a latter day Pythagorean and Stevin a latter day Archimedes, that the early-sixteenth-century anatom ists were only following the method of the newly discovered works of Galen, and the naturalists were tracking down the mysteries of Aristotle's History of Animals, that we have accepted the fact that?however mis guided in its expressed purpose?humanism had a genuinely vital contri bution to make to early modern science. And indeed there are few impor tant aspects of sixteenth-century science which are not enriched with humanist learning and Greek discovery. Aside from magnetism?itself a part of natural magic which drew on the ancients for some of its inspira tion?only chemistry seems to have escaped the prevailing humanist influence, pursuing new ideas and methods without apparent benefit from Greek theory and practice. Indeed, it is possible to argue that the exaggerated mysticism associ ated with alchemy was only possible because of the lack of associated Greek rationalism which might have acted as a counterweight to the accumulated irrationalism of centuries. True, the Greek theory of matter, with its transmutable elements constituting the universe from the time of Aristotle, lies at the basis of the more philosophic part of alchemical theory, as Hopkins long ago pointed out.1 And Aristotle's theory of matter could be used to support the possibility of transmutation, though few chemists were interested in so using it before the development of theoretical chem istry in the early seventeenth century. But by and large chemistry drew what historical tradition it possessed from the immediate, rather than from the remote, past, in spite of the bogus historicism which permitted the attribution of modern works to authors long dead. The most obviously rational part of sixteenth-century chemistry would

The Life and Labours of John Mercer, F.R.S.

THE subject of this memoir was one of the most remarkable men of his time. A son of the soil, and almost wholly self-taught, he effected what was practically a revolution in one of our staple industries by his discoveries in technical chemistry and by his application of chemical principles to the dyer's art. With no laboratory training other than that which he gave himself, he by his skill and sagacity as an experimentalist added enormously to the resources of a great industry: owing nothing to academies, and uninfluenced by schools of learning, he made himself master of the chemical philosophy of his time, and by the acuteness and originality of his speculations he has permanently influenced the development of theoretical chemistry. In Lancashire, the scene of his work, the name of John Mercer is held in hardly less esteem than that of John Dalton; and probably to many people in Cottonopolis the director of the Oakenshaw Print-Works was a far more important personage than the old Quaker in George Street, who gave lessons in the New Systern of Chemical Philosophy at the rate of half-a-crown an hour. The Atomic Theory has doubtless contributed much to the intellectual greatness of Manchester, and Manchester men are not ungrateful: they have named one of their streets after its illustrious author. Still calicoes and calico-printing are what they have to live by, and although they have not yet, so far as we know named a street after John Mercer, they have shown, by the widespread adoption of his processes, a very practical appreciation of the value of his labours. The Life and Labours of John Mercer, F.R.S. By Edward A. Parnell. (London: Longmans and Co., 1886.)