The orientation and bonding of 4,4'-biphenyldiisocyanide (BPDI) adsorbed by solution on Au(111) has been examined by polarization dependent photoemission and inverse photoemission. The highest occupied molecular orbital to lowest unoccupied molecular orbital gap for BPDI is about 10.8 eV, with the Fermi level nearly midgap. The electronic structure of isocyano-functionalized polyphenyls suggests that they are better dielectrics than thiol-functionalized polyphenyls.