Balsukuri, NareshNareshBalsukuriManav, NehaNehaManavLone, Mohsin Y.Mohsin Y.LoneMori, ShigekiShigekiMoriDas, AritraAritraDasSen, PratikPratikSenGupta, ItiItiGupta2025-08-312025-08-312020-05-0110.1016/j.dyepig.2020.1082492-s2.0-85078699159http://repository.iitgn.ac.in/handle/IITG2025/24166This work is focused on the design and synthesis of donor-acceptor pairs comprising of aza-BODIPY and tetraphenylethene (TPE) fluorogens with large pseudo Stokes shifts (386–424 nm). Femtosecond transient absorption spectroscopy, single crystal X-ray technique and TD-DFT studies were used to get more insight about their spectral behavior. As compared to the tetra-phenylaza-BODIPY, the four aza-BODIPYs exhibited 50–90 nm red shifted absoprtion and emission spectra. When the donor-acceptor architectures were excited at 300 nm, the aza-BODIPY unit emitted strong fluorescence in red region. This suggested an intramolecular energy transfer between donor (TPE) and the aza-BODIPY acceptor; with 81–90% energy transfer efficiencies. Femtosecond transient absorption studies also supported energy transfer process in the molecules, with 3.7 ps time constant associated with it. Aggregation studies in THF/n-heptane solution showed hypsochromic shifts in the aggregated form; X-ray packing structures indicated H-type aggregates (slip angle > 54.7°) in the solid state. Scanning electron microscopy (SEM) measurement revealed 200–700 nm size sphere shaped structures in the aggregated forms.falseAggregation studies | Aza-BODIPY | Donor-acceptor system | Energy transfer | Pseudo Stokes shifts | TD-DFT | Transient absorptionArticle18733743May 202028108249arJournal26WOS:000519335300046