Table 4. Experimental Photophysical Data of Selected Chromeno[4,3-d]pyrido[1,2-a]pyrimidin-6-ones.

entry	compound	absorptiona λmax,abs (nm)	emissiona λmax,emi (nm)	molar extinction coefficient × 104 (ε) n−π*	Stokes shift Δυ̅ (cm–1)	quantum yield (Φ)b
1	8a	208, 305	350	0.52095	4216	0.0403
2	8d	209, 305	352	0.63869	4378	0.0213
3	8f	208, 305	353	0.63414	4458	0.0186
4	8g	212, 305	352	0.88867	4378	0.0125
5	8i	210, 305	353	0.75602	4458	0.0176
6	8j	212, 305	352	0.62899	4378	0.0363
7	8l	212, 305	353	0.93248	4458	0.0088
8	8m	210, 304	352	0.59099	4486	0.0459
9	8n	206, 305	352	0.64208	4378	0.0357
10	8o	210, 306	351	0.81409	4190	0.0386
11	8p	210, 305	353	0.75602	4458	0.0148
12	8q	208, 306	357	0.60639	4668	0.0124

^aRecorded at 300 K in CH₃CN.

^bCalculated with Tryptophan as a reference standard (Φ_st = 0.16).