Synthesis and Structure-Photophysics Evaluation of 2-N-Amino-quinazolines: Small Molecule Fluorophores for Solution and Solid State.

2- N -aminoquinazolines were prepared by consecu-tive S N Ar functionalization. X-ray structures display the nitrogen lone pair of the 2- N -morphilino group in conjugation with the electron defi-cient quinazoline core and thus representing electronic push-pull sys-tems. 2- N -aminoquinazolines show a positive solvatochromism and are flu-orescent in solution and in solid state with quantum yields up to 0.73. Increase in electron donor strength of the 2-amino substituent causes a red-shift of the intramolecular charge transfer (ICT) band (300-400 nm); whereas the photoluminescence emission maxima (350-450 nm) is also red-shifted significantly along with an enhance-ment in photoluminescence efficiency. HOMO-LUMO energies were estimated by a combination of electrochemical and photophysical methods and correlate well to those obtained by computational methods. ICT properties are theoretically attributed to an excitation to Rydberg-MO in SAC-CI method, which can be interpreted as n-p* ex-citation. 7-Amino-2- N -morpholino-4-methoxyquinazoline responds to acidic conditions with significant increases in photoluminescence in-tensity revealing a new turn-on/off fluorescence probe.