TY - JOUR T1 - Five concomitant polymorphs of a green fluorescent protein chromophore (GFPc) analogue: understanding variations in photoluminescence with pi-stacking interactions JF - Acta Crystallographica Section B-Structural Science Crystal Engineering and Materials Y1 - 2020 A1 - Mali, Bhupendra P. A1 - Dash, Soumya Ranjan A1 - Nikam, Shrikant B. A1 - Puthuvakkal, Anisha A1 - Vanka, Kumar A1 - Manoj, Kochunnoonny A1 - Gonnade, Rajesh G. KW - green fluorescent protein KW - hydrogen bonds KW - isostructurality KW - photoluminescence KW - pi-stacking KW - Polymorphs AB -

The synthetically modified green fluorescent protein chromophore analogue 3,4,5-trimethoxybenzylidene imidazolinone (1) yielded five polymorphs (I, II, III, IV, V) concomitantly irrespective of the solvent used for crystallization. The pentamorphic modification of 1 is solely due to the interplay of iso-energetic weak intermolecular interactions in molecular associations as well as the conformational flexibility offered by a C-C single bond, which connects the electron-deficient moiety imidazolinone with the electron-rich trimethoxybenzylidene group. A common structural feature observed in all the polymorphs is the formation of a `zero-dimensional' centrosymmetric dimeric unit through a short and linear C-H center dot center dot center dot O hydrogen bond engaging phenyl C-H and imidazolinone carbonyl oxygen. However, the networking of these dimeric units showed a subtle difference in all the polymorphs. The 2D isostructurality was observed between polymorphs I, II and III, while the other two polymorphs IV and V revealed only `zero-dimensional' isostructurality. The different fluorescence emissions of Form I (blue) and Forms II to V (yellow) were attributed to the differences in pi-stacking interactions. It shows that one can modulate the photophysical properties of these smart materials by slightly altering their crystal structure. Such an approach will aid in developing new multi-colour organic fluorescent materials of varying crystal structures for live-cell imaging and fluorescent sensing applications.

VL - 76 U3 -

Foreign

U4 -

2.048

ER -