Polymorphism and Pseudopolymorphism of the [Ni(4-Methylpyridine)₄(NCS)₂] Werner Complex, the Compound that Led to the Concept of “Organic Zeolites”

Abstract

The inclusion chemistry of the title complex was revisited in the context of three topical problems of present-day crystal engineering: conventional and pseudo-polymorphism, the design of organic zeolite mimics, and the creation of "third generation" porous metal-organic frameworks. The crystal structures of dense (R) and microporous (β) polymorphs of the complex were redetermined and two new crystal structures were studied: β-and γ-inclusion phases of the complex (1:1 and 1:2 host-to-guest ratio, respectively) with benzene as the simplest aromatic guest. Although both the β-and γ-crystal architectures display a remarkable adaptability toward inclusion of various guests, the mechanisms of this adaptability are essentially different. The microporous β-phase is capable of expanding by 14.5% in response to the size of the included guest or variations in temperature. This flexibility is the highest ever observed for a metal-organic microporous framework and is responsible for the zeolitic behavior of the material. In contrast, the γ-phase shows an ability to transform to a number of architectures that are topologically similar but crystallographically different.

Syntheses, Structures, and Properties of Phosphorescent Iridium(III) Complexes Containing N‐Heterocyclic Carbene Ligands

“…Interestingly, by layering MeOH above a CH 2 Cl 2 solution containing 1 (PF 6 ), two types of crystals emerged, which were designated as 1a and 1b , respectively. Except for 1 + cations (Figure S1) and PF 6 − anions, both crystals include the respective solvent molecules with CH 2 Cl 2 in crystal 1a and MeOH in 1b , revealing the presence of pseudo‐polymorphs . It was noted that inclusion of the solvent molecules appears selective.…”

Polymorphism and reactivity of [Ni(pyridine)4(NCS)2]: Two new supramolecular isomers and one macro-ionic derivative

“…[11e]. To our best of knowledge, only one example of pseudopolymorphism about thiocyanate complexes was reported [2], the formation of forms 1 and 2 and together with the reported form, represents the first solvent-free trimorphs of this system. Because the specific forms have unique rotation of pyridine rings with different dihedral angles between the pyridine rings and the mean plane of the four coordinated pyridine N atoms, this polymorphism can be assigned to conformational polymorphism [12f,12g,12h].…”

“…However, research efforts are primarily focused on their synthesis, magnetism and coordination isomerism. Noticeably, despite great significance as functional solid materials, polymorphism of thiocyanate complexes remains little explored [2]. Furthermore, very little is also known about the reactivity of these complexes in comparison with the extensive knowledge of other pseudohalide complexes, such as azide complexes [4].…”

“…Thiocyanate (or isothiocyanate) complexes have attracted a great attention due to their structural versatility and potential for development of optical, electrical, organic zeolite, magnetic and conductive materials [1][2][3]. However, research efforts are primarily focused on their synthesis, magnetism and coordination isomerism.…”

Crystallization Behavior of Coordination Polymers. 1. Kinetic and Thermodynamic Features of 1,3-Bis(4-pyridyl)propane/MCl2 Systems

“…The counterpart of ligands shows an even wider variety of choices being based on multifunctional organic or inorganic moieties, displaying diversified local stereochemistries supposedly able to force the self-assembling of MOFs to follow a pre-established structural motif as wished by crystal engineers. [22][23][24] Many structurally relevant MOFs which do have promising properties for key technological applications and high commercial value 25 have been synthesized starting from nitrogen-based multifunctional ligands. 3,16c,d,26 Among them, pyridine-based ligands differing in length, flexibility, and conformational freedom produced a variety of supramolecular networks with different metal cations.…”