Crystallisation kinetics of organic compounds; quinacridone derivatives as UV-active probes of solution state pre-nucleation phenomena

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Shanahan, Louise
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University College Cork
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An ideal crystallisation process is predictable and reproducible; a less than simple ask. The influence of pre-nucleation molecular interactions in solution on the crystallised phase obtained has been highlighted. To improve our understanding of crystallisation outcomes, comprehending solution-state pre-nucleation phenomena is desirable. Previously, the aggregation of di- and tetra(alkoxy) derivatives of quinacridone 1 has been studied in solution using UV-vis spectroscopy: λmax shifts were observed for certain derivatives under conditions of increased concentration or reduced temperature. Correlation of IR spectra of aggregates in solution, with phases of unsubstituted quinacridone 1 in the solid-state, led to proposed structures of these species in solution. The scope of the previous work in this area was herein extended to a wider range of alkoxyquinacridones and solvents including: 2-MeTHF, NMP, DMF and DMSO. Tetra(alkoxy)quinacridones featuring pentyloxy, octyloxy, dodecyloxy, elaidyloxy or oleyloxy chains, as well as 2,9-di-(2-undecyltridecyl-1-oxy)quinacridone, were prepared as probes of molecular interactions in solution. Analysis of these compounds by UV-vis spectroscopy revealed concentration and temperature dependent bathochromic shifts in solvents such as 2-MeTHF and toluene. Aggregation was found to be solvent, concentration, temperature and substrate dependent. Aggregation of tetra(alkoxy)-quinacridones in 2-MeTHF was modulated by addition of hydrogen bonding competing solvents such as NMP. Other highlights of the work include the selective acquisition of various phases of quinacridone 1 from N,N’-disubstituted quinacridones, with MEM or SEM removable groups. Distinctive solid-state forms of 2,3,9,10-tetra(dodecyloxy)quinacridone were also obtained, distinguished by colour and IR spectroscopy, as well as unusual disparity in their 1H NMR spectra. We also report a novel synthesis of unsubstituted quinacridone 1 and N,N’- dialkylated quinacridones, employing aryne chemistry. Representing a mild preparation, the sterically un-hindered target, N,N’-dimethylquinacridone, was obtained in particularly high yield applying this methodology. Full abstract can be viewed on
Quinacridones , Solvatochromic compounds , Solution-state aggregation , Solid-state forms
Shanahan, L. 2019. Crystallisation kinetics of organic compounds; quinacridone derivatives as UV-active probes of solution state pre-nucleation phenomena. PhD Thesis, University College Cork.