Zero-field splittings of the emitting levels of the title compounds were measured by ODMR. For complexes of the type Zn(X-PhS)₂(phen) resonances of the³ππ^* phosphorescing levels were observed for X=F₅, 4-Cl, 4-CH₃. For X=4-Cl, resonances were detected for the³LLCT emitting manifold also. For X=4-CH₃O, resonances were detected only for the³LLCT emitting states. A model invoking mixing between the two types of states is proposed that satisfactorily accounts for the dependences of the properties of the emitting manifolds on the donating ability of the X substituent.

The magnetic field dependence of CIDNP was measured for the photolysis of benzaldehyde. At high and low fields, respectively, the CIDNP behavior is satisfactorily interpreted by theS-T_o andS-T_- mixing of radical pair mechanism (RPM). At around 325 mT the CIDNP of the aldehyde proton is emissive, which cannot be interpreted by RPM. In order to understand this anomalous behavior, we observe the dynamic nuclear polarization.

The DNP sign shows that the cross-relaxation mechanism of the intermediate free radical is δm= 2. With this result, the emissive CIDNP at 325 mT is interpreted by the triplet mechanism (TM) with cross-relaxation-induced polarization transfer from electron spin to nuclear spin.

Further, the time-resolved DNP is observed with laser excitation and switching of microwaves. With pulse excitation, the features of CIDNP and DNP are different from that with continuous light excitation. This is interpreted as due to the associated increase of the initial concentration of the ketyl radical. From the time dependence of the DNP intensity, the lifetime of the ketyl radical is estimated to be of the order of hundreds of nanoseconds.