To gain insight into the optical properties of donor-functionalized pyrenes, we synthesize a series of four donor-substituted pyrenes of increasing donor strength (see Figure ). 1-Bromopyrene serves as the starting material for all four target compounds, while the donors are attached via straightforward C-N and C-C cross-coupling reactions (see Supporting Information for synthetic details). We perform density functional theory (DFT) calculations on the M062X-GD3/def2-TZVP level of theory to determine the dipole moment µ of the four synthesized donor-functionalized pyrenes (see Table and SI for further details). PyPhCz and PyFlCz exhibit similar µ of 1.75 D and 1.76 D, respectively, while PyCz yields µ = 1.98 D. Utilizing phenoxazine as an even stronger donor than Cz, PyPox yields a large µ = 2.67 D (see Figure ). To confirm the results from our DFT calculations, we perform UV-Vis and photoluminescence spectroscopy (see Figure and). The absorption spectra of PyCz and PyPox in dichloromethane (DCM) solution both exhibit sharp maxima at 341 nm, which is typical for an isolated pyrene segment, indicating that the πconjugation of the pyrene does not extend into the donor units. In PyPhCz and PyFlCz the aromatic linkers between the pyrene and the Cz units seem to partake in the pyrene conjugation, as their absorption spectra are broadened and the maxima are redshifted with maxima at 347 and 348 nm, respectively (see Figure ). CT character the examined system exhibits (see Supporting Information). PyFlCz, PyPhCz, and PyCz display only a small increase of the Stokes shift for non-polar solvents up to DCM. For solvents of greater polarity, there is a threshold, upon which the Stokes shift dramatically increases. This partitioning of smaller and larger slopes before and beyond a threshold is typical for hybridized local and charge transfer (HLCT) behavior. An HLCT state is a combination of a locally excited (LE) state, which is dominant in non-polar solvents, and a CT state, which is more distinct in polar environment. For our four compounds the pyrene core presumably serves as the electron acceptor in the case of charge-transfer. The linear slopes of these compounds increase with the donor strength from PyFlCz over PyPhCz to PyCz. The increasing strength of the donors successively enhances the CT character in the respective compound. By contrast, PyPox shows a continuous linear dependency of the Stokes shift and f(ε,n) with a steep incline across the entire range of solvents, which implies a pure CT excited state independent of the surrounding medium.