CCL: UV-VIS spectra values obtained computationally are different (TDDFT & CIS) for different concentrations



Hi,
Greetings.

I have a UV-Vis spectra of a compound at different concentrations. (10-2M to 10-5M)

At higher concentration( ~10-2 M), the experimental peaks match well with TDDFT/6-31+G* values (400nm), whereas at lower concentration (~10-5M), the experimental peaks match with CIS/6-31+G* values (280 nm).

The IR values obtained experimentally and computationally matches well (for DFT values).

I would be thankful if someone could help me in knowing as to which value (TDDFT or CIS) to consider for assigning UV-VIS spectra computationally.

thanking you.
ashu