Engineering Molecular Crystals: Backbreaking, yet Gratifying

Abstract

A personal account of the hurdles encountered when studying each of the aspects of crystal engineering, namely, designing, building, and using crystal structures. Examples are given to illustrate the “backbreaking” nature of the crystal engineering endeavor, as well as the limitations of our current abilities to understand, engineer, and maintain molecular crystals.

Modulation of coordination in pincer-type isonicotinohydrazone Schiff base ligands by proton transfer

“…1.477 (9) 1.499 (4) N5-C19/ or C14 1.143(13) 1.143(4) N1-N2 1.382 (7) 1.372 (3) N6-C20/ or C15 1.158(14) 1.148(4) N2-C2 1.282 (9) 1.288(3) S1-C19/ or C14 1.643(11) 1.667(4) C2-C13 1.467 (9) 1.496 (4) S2-C20/ or C15 1.650(13) 1.649 (3) Hg1-S1-C19/ or C14 100.2(4) 97.6(1) Hg1-S2-C20/ or C15 96.7(3) 99.7(1) O1-Hg1-N3-C7 171.1 (5) 175.9(2) C1-N1-N2-Hg1 13.2 (7) 2.6(3) N1-N2-Hg1-N3 169.0(5) 179.0(2) Fig. 3.…”

“…The crystal engineering is not a trivial problem and still many aspects of controlling crystal growth need to be studied and it is not easy to predict the outcome of crystallization. [1][2][3][4][5][6] In fact, a major challenge using polydentate chelating-bridging building blocks in the synthesis of metal coordination compounds is the unpredictability of the structure of the products which may depend on several factors such as the nature of the ligands used, the oxidation state, geometry, and size of the metal centers, the metal-to-ligand ratio, etc. [7][8][9] Hydrazone-pyridine based chelating ligands are known N,N,O pincer type ligands.…”

Understanding stress-induced disorder and breakage in organic crystals: beyond crystal structure anisotropy

“…The interplay between crystal form and surface, is therefore essential to the design, synthesis, and development of new solid materials with targeted chemical and physical properties. 4,[18][19][20] One such aspect of increasing interest involves the mechanical behaviour of organic solids, in particular the ability of a crystal to bend, move, break or heal. [21][22][23][24][25][26][27][28][29] These characteristics play a signicant role in the secondary manufacturing of Active Pharmaceutical Ingredients (APIs) such as milling and tableting of pure materials, and blending with excipients.…”

Chiral Cocrystal Solid Solutions, Molecular Complexes, and Salts of N-Triphenylacetyl-l-Tyrosine and Diamines

“…The creation of cocrystals is in the interest of both materials and pharmaceutical sciences. It is known that cocrystallization is one of the methods used in pharmacy in tuning properties of materials [29,30]. One of the challenges in this field is obtaining materials that allow the most optimal use of active substances.…”