Sinisa Vukovic Thank You.

CT is a term used for adducts, i.e. systems formed by a donor and an acceptor. An example can be considered the adduct between NH3 (donor) and BF3 (acceptor). As a consequence of the interaction, a fraction of the electron-rich donor is transferred to the acceptor. This reduces the net electron population on the donor and increase the electron population on the acceptor. If the synthons were both neutral, the donor will carry a positive charge in the addcut, while the acceptor a negative charge.

https://en.wikipedia.org/wiki/Charge-transfer_complex

Charge distributions, and hence Mulliken population as well, allow to evaluate the charge on the atoms of the interacting donor and acceptor and evaluate the charge transfer. A typical type of acceptors is represented by dihalogens. Dihalogens X2 interact with a number of donors, such as Chalcogen donors >L=E (E = S, Se, Te) To form CT adducts >L=E·X2. An example can be found here:

Article Formation of T-Shaped versus Charge-Transfer Molecular Adduc...

Similarly, pnictogen donors form CT adducts, such as Py·I2 (Py = pyridine):

Article Reactions of pyridyl donors with halogens and interhalogens:...

Often, CT interactions alter the MO structure, therefore resulting in peculiar absorption bands known - of course - as CT bands.

https://ur.booksc.eu/book/4096875/d2e57e

Please not that charge distribution can be used to evaluate the degree of bond polarisation within a compound, as in the case discussed above of H2O (although H2O should not be defined as a CT compound, since it is not exactly a Lewis adduct).

On the contrary, coordinated halides in metal complexes form CT interactions, and the resulting absorption bands are - in fact - classified as CT absorption bands. This topic has already been dealt with in researchgate:

https://www.researchgate.net/post/How-can-one-say-an-absorption-band-is-of-charge-transfer-CT-in-nature

I hope this may help.