A heterotrinuclear [Pt$_{2}$Fe] spin crossover (SCO) complex was developed and synthesized employing a ditopic bridging bpp-alkynyl ligand L and alkynyl coordinated PtII terpy units: [Fe$^{II}$(L-Pt$^{II}$)$_{2}$]$_{2}$(BF$_{4}$)$_{2}$ (1). We identified two different types of crystals of 1 which differ in their molecular packing and the number of co-crystallized solvent molecules: 1$^H$ (1·3.5CH$_{2}$Cl$_{2}$ in P$\bar{1}$ with combining macron]) and 1$^{L}$ (1·10CH$_{2}$Cl$_{2}$ in C$_{2}$/c); while 1$^{L}$ shows a reversible SCO with a transition temperature of 268 K, the analogous compound 1$^{H}$ does not show any SCO and remains blocked in the HS state. The temperature-dependent magnetic properties of 1$^{H}$ and 1$^{L}$ were complementarily studied by Mössbauer spectroscopy. It has been shown that 1$^{L}$ performs thermal spin crossover and that 1$^{L}$ can be excited to a LIESST state. The vibrational properties of 1 were investigated by experimental nuclear resonance vibrational spectroscopy. The experimentally determined partial density of vibrational states (pDOS) was compared to a DFT-based simulation of the pDOS. The vibrational modes of the different components were assigned and visualized. In addition, the photophysical properties of 1 and L-Pt were investigated in the solid state and in solution. The ultrafast transient absorption spectroscopy of 1 in solution was carried out to study the PL quenching channel via energy transfer from photoexcited Pt$^{II}$ terpy units to the Fe$^{II}$-moiety.