Polymorphs of Molecular Crystals

Caira, Mino R.

doi:10.1016/b978-0-12-409547-2.12605-8

Cited by 4 publications

(2 citation statements)

References 101 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Polymorphism is commonly divided into four main types, viz. packing, synthon, conformational, and tautomeric, though they are not mutually exclusive and the concept of tautomeric polymorphism is somewhat controversial. ,, Cruz-Cabeza and Bernstein opined that polymorphs should be termed conformational only if the conformations in the different forms belong to different gas-phase potential-energy minima . Under this definition, they estimated that 36% of CSD polymorphs were conformational.…”

Section: Fundamental Sciencementioning

confidence: 99%

A Million Crystal Structures: The Whole Is Greater than the Sum of Its Parts

2019

View full text Add to dashboard Cite

The founding in 1965 of what is now called the Cambridge Structural Database (CSD) has reaped dividends in numerous and diverse areas of chemical research. Each of the million or so crystal structures in the database was solved for its own particular reason, but collected together, the structures can be reused to address a multitude of new problems. In this Review, which is focused mainly on the last 10 years, we chronicle the contribution of the CSD to research into molecular geometries, molecular interactions, and molecular assemblies and demonstrate its value in the design of biologically active molecules and the solid forms in which they are delivered. Its potential in other commercially relevant areas is described, including gas storage and delivery, thin films, and (opto)electronics. The CSD also aids the solution of new crystal structures. Because no scientific instrument is without shortcomings, the limitations of CSD research are assessed. We emphasize the importance of maintaining database quality: notwithstanding the arrival of big data and machine learning, it remains perilous to ignore the principle of garbage in, garbage out. Finally, we explain why the CSD must evolve with the world around it to ensure it remains fit for purpose in the years ahead.

show abstract

Section: Fundamental Sciencementioning

confidence: 99%

A Million Crystal Structures: The Whole Is Greater than the Sum of Its Parts

2019

View full text Add to dashboard Cite

show abstract

“…Many compounds possess the ability to form polymorphs (Rolf, 2006;Caira, 2017) and polymorphism and disorder are well established in N-benzylideneaniline compounds. Homodisubstituted benzylideneaniline compounds such as N-(4chlorobenzylidene)-4-chloroaniline (Bernstein & Schmidt, 1972;Bernstein & Izak, 1976) and N-(4-methylbenzylidene)-4methylaniline (Bar & Bernstein, 1977, 1982Bernstein & Izak,1976) exist in dimorphic and trimorphic forms, respectively.…”

Section: Chemical Contextmentioning

confidence: 99%

Synthesis, crystal structure and Hirshfeld surface analysis of the orthorhombic polymorph of 4-bromo-N-(4-bromobenzylidene)aniline

et al. 2023

View full text Add to dashboard Cite

The crystal structure of the title compound, C13H9Br2N [systematic name: (E)-N,1-bis(4-bromophenyl)methanimine], is a second polymorph (Form II) crystallizing in the orthorhombic space group Pccn. The first polymorph (Form I) crystallizes in the monoclinic space group P21/c [Bernstein & Izak (1975). J. Cryst. Mol. Struct. 5, 257–266; Marin et al. (2013). J. Mol. Struct. 1049, 377–385]. The molecule is disordered about an inversion center situated in the middle of the C=N bond, similar to the situation in the monoclinic polymorph: the C=N bond length is 1.243 (7) Å. In the crystal, molecules stack along the b-axis direction and are linked by C—H...π interactions. The interatomic contacts in the crystal for both polymorphs were studied by Hirshfeld surface analysis and have notable differences. The solid-state fluorescence spectrum of Form II shows an emission peak at ca 469 nm. The two-photon absorption coefficient measured from the open aperture Z-scan technique is 1.3 × 10 −11 m W−1, hence, Form II shows optical limiting behaviour.

show abstract