J. Appl. Cryst.の発刊に際して

2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Kirk-Othmer Encyclopedia of Chemical Technology数据库介绍及实例

We have recently described a remarkable new way of exploring packing modes and intermolecular interactions in molecular crystals using a novel partitioning of crystal space. These molecular Hirshfeld surfaces reflect intermolecular interactions in a novel visual manner, offering a hitherto unseen picture of molecular shape in a crystalline environment. The surfaces encode information about all intermolecular interactions simultaneously, but sophisticated interactive graphics are required in order to extract the information most efficiently. To overcome this we have devised a two-dimensional mapping which summarizes quantitatively the nature and type of intermolecular interaction experienced by a molecule in the bulk, and presents it in a convenient graphical format. The mapping takes advantage of the triangulation of the Hirshfeld surfaces, and plots the fraction of points on the surface as a function of the closest distances from the point to nuclei inside and outside the surface.
In this manner all interaction types (for example, hydrogen bonding, close and distant van der Waals contacts, C–H⋯π interactions, π–π stacking) are readily identifiable, and it becomes a straightforward matter to classify molecular crystals by the nature of interactions, and to rapidly identify similarities and differences which can become obscured when examining crystal packing diagrams. These plots are a novel visual representation of all the intermolecular interactions simultaneously, and are unique for a given crystal structure and polymorph. Applications to a wide variety of molecular crystals and intermolecular interactions are presented, including polymorphic systems, as well as crystals where Z′ > 1.

Fingerprinting intermolecular interactions in molecular crystals

The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

The Halogen Bond

In the title compound, C18H15NO3, the pyridine-2,6-dione ring adopts an envelope conformation. The phenyl ring lies approximately perpendicular to the mean plane of the pyridine-2,6-dione ring [dihedral angle = 81.5 (1)°], while the methoxy­phenyl ring is tilted to the same plane by a dihedral angle of 34.8 (1)°. Inter­molecular C—H⋯O inter­actions link the mol­ecules into chains along [100].

https://journals.iucr.org/e/issues/2009/06/00/bi2366/bi2366.pdf

4-(4-Methoxy-phen-yl)-1-phenyl-pyridine-2,6(1H,3H)-dione.

The title compound, $C_{12}H_{18}O_4S_2$, exhibits fungicidal activity. A short $S\cdot\cdot\cdot S$ intermolecular contact $[3.576(3)\AA]$ is observed in the crystal structure, which is further stabilized by $C-H\cdot\cdot\cdot O$ intermolecular interactions, forming molecular chains along the b axis.

Diisopropyl (1,3-dithiolan-2-ylidene)malonate

In the title compound, $C_{13}H_{9}FO_{3}$, the dihedral angle between the benzene rings is 82.1 (1) Angstrom. The crystal structure is mainly stabilized by carboxylic acid dimers involving O-H...O hydrogen bonds, along with the formation of weak but highly directional intermolecular C-H...O and C-H...F interactions.

4-Fluoro-3-phenoxybenzoic acid

Finding stable analogues of three-dimensional (3D) lead halide perovskites has motivated the exploration of an ever-expanding repertoire of two-dimensional (2D) counterparts. However, the bandgap and exciton binding energy in these 2D systems are generally considerably higher than those in 3D analogues due to size and dielectric confinement. Such quantum confinements are most prominently manifested in the extreme 2D realization in (A)mPbI4 (m = 1 or 2) series of compounds with a single inorganic layer repeat unit. Here, we explore a new A-site cation, 4,4'-azopyridine (APD), whose size and hydrogen bonding properties endow the corresponding (APD)PbI4 2D compound with the lowest bandgap and exciton binding energy of all such compounds, 2.19 eV and 48 meV, respectively. (APD)PbI4 presents the first example of the ideal Pb-I-Pb bond angle of 180°, maximizing the valence and conduction bandwidths and minimizing the electron and hole effective masses. These effects coupled with a significant increase in the dielectric constant provide an explanation for the unique bandgap and exciton binding energies in this system. Our theoretical results further reveal that the requirement of optimizing the hydrogen bonding interactions between the organic and the inorganic units provides the driving force for achieving the structural uniqueness and the associated optoelectronic properties in this system. Our preliminary investigations in characterizing photovoltaic solar cells in the presence of APD show encouraging improvements in performances and stability.

Realizing the Lowest Bandgap and Exciton Binding Energy in a Two-Dimensional Lead Halide System.

MULTAN is the most widely used package for structure determination. However, there are situations where even after utilizing all possible built-in routes the solution is not reached and these become “difficult structures”. If such a structure (a) has one or more heavy atoms, (b) is “chicken-wire” with predominant aromatic character, (c) has weak diffraction data, the new approaches discussed will lead to a unique structure solution by introducing simple, economic and time saving ideas into the MULTAN package.

T. N. Guru Row

Papers

4-(4-Methoxy-phen-yl)-1-phenyl-pyridine-2,6(1H,3H)-dione.

Diisopropyl (1,3-dithiolan-2-ylidene)malonate

4-Fluoro-3-phenoxybenzoic acid

Realizing the Lowest Bandgap and Exciton Binding Energy in a Two-Dimensional Lead Halide System.

Solution of difficult crystal structures: new, simple, economic and time saving approaches