Best practices in `0 K' DFT energy calculations on mol­ecular crystal structures

This article describes best practices for `zero Kelvin' energy calculations on mol­ecular crystals and is targeted for non-experts who would like to perform their own calculations or assess the accuracy and validity of such calculations reported in the scientific literature.

Crystal and electronic structure of heteroanionic praseodymium chloro­silicate Pr₃Cl₅[SiO₄]

A new heteroanionic rare-earth chloro­silicate, Pr₃Cl₅[SiO₄], was synthesized by a self-flux-assisted high-tem­per­a­ture reaction. Single-crystal X-ray diffraction shows that it crystallizes in the ortho­rhom­bic space group Pnma and contains orientationally disordered discrete [SiO₄]⁴⁻ tetra­hedra within a three-dimensional Pr–Cl/O framework. Electronic structure calculations indicate a wide indirect band gap of ∼4.53 eV, with bonding dominated by strong Si—O inter­actions.

Effect of mol­ecular perturbation on co­crys­tal formation: theo­phyl­line and its 8-halo analogues with flavonoids

The tendency for alkaloid–flavonoid co­crys­tal formation is found to be markedly different for theo­phyl­line (Tph) com­pared to its 8-halo analogues. Through screening with 13 common flavonoids, Tph is found to form co­crys­tals with six flavonoids, whereas 8-Cl-Tph and 8-Br-Tph each form co­crys­tals with just two, myricetin and kaempferol. The weakening of the alkaloid N9 atom as a hy­dro­gen-bond acceptor towards the hy­dro­gen-bond-donor-rich flavonoids may play a role in this differing tendency.

Salt forms of the monoazo dye Mordant Orange 1

The crystal structures of eight salt forms of the carboxyl­ate-functionalized monoazo dye Mordant Orange 1 are pre­sent­ed and discussed, primarily in terms of their coordination behaviour.

Weak inter­actions defining the crystal packing in the sterically demanding com­pound 1-(3-methyl­phen­yl)-2-(4-nitro­phen­yl)-4,5-di­phenyl-1H-imid­azole

Crystals from a tetra­substituted 1H-imid­a­zole were obtained and theoretical calculations were carried out to determine electronic and structural properties. Weak inter­actions define the crystal packing in this sterically demanding com­pound. The nitro groups play a key role by their influence on the polarization of the mol­ecule.