Complementary Host\nBehavior of Fluorenone-Derived\nHost Compounds during Crystallization Processes from Mixed Anilines

Two fluorenone-derived compounds, namely 9,9′-(1,4-phenylene)bis(fluoren-9-ol)\n(<b>H1</b>) and 9,9′-(ethyne-1,2-diyl)bis(fluoren-9-ol)\n(<b>H2</b>), were examined for their host behavior in potential\nguest solvents aniline, <i>N</i>-methylaniline and <i>N</i>,<i>N</i>′-dimethylaniline (ANI, NMA and\nDMA). Single solvent crystallization experiments demonstrated that <b>H1</b> formed complexes with ANI (host/guest ratio 1:1) and DMA\n(1:2), while <b>H2</b> included all three solvents, ANI (1:2),\nNMA (1:1) and DMA (2:1). Single crystal X-ray diffraction analyses\nshowed that all complexes were stabilized by means of classical (host)O–H···N(guest)\nhydrogen bonds in addition to other short contacts. Equimolar binary\nguest competition experiments with <b>H1</b> revealed an extremely\nhigh host selectivity for DMA (ANI/DMA and DMA/NMA experiments furnished\ncrystals with >91% DMA), while the experiment with all three anilines\npresent also resulted in a complex with an overwhelming amount of\nDMA (88.3%). <b>H2</b>, on the other hand, selected ANI preferentially\nin equimolar ANI/NMA and ANI/DMA solutions (93.5 and 66.1% ANI), while\nthe ternary guest experiment also showed an increased affinity for\nANI (72.4%). In binary guest competition experiments in which the\nguest concentrations were varied, <b>H1</b> displayed, once\nmore, significant selectivities toward DMA (and ANI in its absence),\nand the selectivity coefficients (<i>K</i>) calculated were\noftentimes >10, implying that separations of many of these mixtures\nare feasible on a practical platform using supramolecular chemistry\nstrategies. Furthermore, <b>H2</b> demonstrated an ability to\nextract large amounts of ANI from 80:20 ANI/NMA, and 60:40 and 80:20\nANI/DMA mixtures. Both thermal and Hirshfield surface analyses were,\nmoreover, carried out on the complexes produced in this work.