  We report electronic structure and physical properties of metal doped picene
as well as selective synthesis of the phase exhibiting 18 K superconducting
transition. First, Raman scattering is used to characterize the number of
electrons transferred from the dopants to picene molecules. The charge transfer
leads to a softening of Raman scattering peaks, which enables us to determine
the number of transferred electrons. From this we have identified that three
electrons are transferred to each picene molecule in the superconducting
doped-picene solids. Second, we report the pressure dependence of Tc in 7 and
18 K phases of K3picene. The 7 K phase shows a negative pressure-dependence,
while the 18 K phase exhibits a positive pressure-dependence which cannot be
understood with a simple phonon mechanism of BCS superconductivity. Third, we
report a new synthesis method for superconducting K3picene by a solution
process with monomethylamine, CH3NH2. This method enables one to prepare
selectively the K3picene sample exhibiting 18 K superconducting transition. The
discovery of suitable way for preparing K3picene with Tc = 18 K may facilitate
clarification of the mechanism of superconductivity.
