This thesis presents a valence band investigation of n-Phenyls on a clean Al(1 1 0) substrate using angle-resolved ultraviolet photoelectron spectroscopy (ARUPS). Monolayers of pristine and alkali metal doped Sexiphenyl and Quinquephenyl molecules have been analysed. Then, a comparison of different n-phenyls in terms of electronic structure vs. chain length was done. The first part is focusing on the well-known para-Sexiphenyl molecule (6P) and the shorter p-Quinquephenyl (5P) exhibiting an odd number of rings. 6P results have been compared to Cu and Ag substrates, where a strong interaction (hybridization) is found. This does not apply to 6P on Al, where only van der Waals forces are acting. This is surprising since the similar geometry of Ag(1 1 0) and Al(1 1 0) suggests a similar behaviour. The two substrates also differ in terms of molecular orientation: while 6P molecules grow perpendicular to the closed paced atomic rows for Ag, they lie parallel on Al(1 1 0) for undoped systems. These discrepancies can be attributed to different substrate electronic structures. However, it is shown that for Al the 6P molecules are still planarised, exhibiting a small tilt. Due to the little interaction between Al and n-phenyls, experimental results are confronted with freestanding molecule DFT calculation and show a very high agreement. Despite the superposition of so called “NonBonding” orbitals with upper -band “bonding/antibonding” orbitals, an undisturbed view of HOMO to HOMO-3 and HOMO-9 to HOMO 11 is given due to the lack of d electrons (Al). Orbital tomography accompanied with orbital reconstruction gives real space images of HOMO, HOMO-1 and HOMO-11 and shows that the HOMO is fully antibonding, whereas HOMO-11 is fully bonding. Besides 6P (and 5P) experiments, the evolution of the upper -band (valence band) for ring numbers going from Benzene to 6P is demonstrated. Here it is shown that the band spread is increasing strongly when going to longer n Phenyls first, but this effect is weakened for longer molecules (beyond n>3). The second part focuses on alkali metal doping: Cs was deposited on 6P monolayers and LUMO + LUMO+1 were filled at room temperature. This was put into contrast to HSA-DFT calculations of freestanding 6P molecules. This was also done with the shorter para Quinquephenyl (5P) and revealed a very high agreement of experimental results and theory for both, changes upon doping and molecule length. Besides 5P and 6P, shorter n-Phenyls were also investigated but for different substrates. Here it is demonstrated that up to Terphenyl (3P) the molecules can only hold two additional electrons (LUMO), whereas in Quaterphenyl (4P) and larger molecules both, LUMO and LUMO+1 were filled.