Acknowledgment SYNTHESIS, CRYSTAL STRUCTURES, AND ELECTRONIC SPECTRA OF (1,8-C 8 H 6 N 2 )Re I (CO) 3 Cl AND [(1,8-C 8 H 6 N 2 )Cu I (DPEPhos)]PF 6 U. Monkowius 1, Y. N. Svartsov 1, T. Fischer 2, M. Zabel 2, H. Yersin 2 Introduction 1 Institut für Anorganische Chemie, Johannes Kepler Universität Linz, A-4040 Linz, Austria 2 Institut für Physikalische Chemie, Universität Regensburg, D Regensburg, Germany Electronic absorption and emission spectroscopy This work was supported by the Bundesministerium für Bildung und Forschung (BMBF) and the Austrian Grid. Conclusions Transition-metal complexes containing 1,10-phenanthroline (phen) ligands frequently display interesting photo- and electro- luminescence and thus are well suited for opto-electronic applications (OLEDs, sensors, etc.). In contrast, there is little known about photophysical properties of complexes with the 1,8-naphthyridine (nap) ligand. Due to the decreased extent of the  - system of the chromophoric moiety, a higher energy of the electronic transitions is expected. To probe the facility to generate luminescent compounds two examples with Re I and Cu I, respectively, were synthesized and characterized by X-ray diffraction, UV/Vis- and emission-spectroscopy. Recent studies with the analogous phen complexes (phen)Re I (CO) 3 Cl and [(phen)Cu I (DPEPhos)] + (DPEPhos = Bis[2-(diphenylphosphino)phenyl]-ether) have demonstrated their applicability in organic light emitting devices. [1] While phen acts as a bidentate ligand in the vast majority of complexes, the nap can establish bidentate, bridging or monodentate patterns of complexation. [2] phennap References [1]F. Li, M. Zhang, G. Cheng, J. Feng, Y. Zhao, Y. Ma, S. Liu, J. Shen, Appl. Phys. Lett. 2004, 84, 148; Q. Zhang, Q. Zhou, Y. Cheng, L. Wang, D. Ma, X. Jing, F. Wang, Adv. Mater. 2004, 16, 432. [2]M. Maekawa, M. Munakata, S. Kitagawa, T. Kuroda-Sowa, Y. Suenaga, M. Yamamoto, Inorg. Chim. Acta 1998, 271, 129. [3]S.-M. Kuang, D. G. Cuttell, D. R. McMillin, P. E. Fanwick, R. A. Walton, Inorg. Chem. 2002, 41, Synthesis Crystal structures monoclinic, P2 1 /c a = (8) Å b = (2) Å c = (10) Å  = (9)° triclinic, a = (8) Å b = (10) Å c = (13) Å  = (14)°  = (14)°  = (13)° Distances [Å]XrayCalculations * Bond angles [°]XrayCalculations * Re1-N12.232(3) N1-Re1-N160.12(10) Re1-N22.236(2) C10-Re1-C (15) Re1-Cl (8) Cl1-Re1-C (10) Re1-C91.921(3) Re1-C (4) Re1-C (3) Distances [Å]XrayCalculations * Bond angles [°]XrayCalculations * Cu1-N (15) N1-Cu1-N258.31(5) Cu1-N (16) P1-Cu1-P (2) Cu1-P (5) N1-Cu1-P (4) Cu1-P (5) N1-Cu1-P (4) Cu1-O13.093(2) max (CHCl 3, log  ) 257 nm (3.63) 297 nm (3.69) 303 nm (3.74) 308 nm (3.72) em (CHCl 3, 300 K) 369 (sh), 388, 407, 430 (sh) nm max (CHCl 3, log  ) 276 nm (4.18) 301 nm (sh, 3.93) 313 nm (sh, 3.79) 415 nm (3.25) em (solid, 300 K) 594 nm max (MeCN, log  ) 224 nm (4.80). 301 nm (4.22) em (solid, 300 K) 638 nm DFT Calculations * * Quantum-chemical calculations have been carried out using density functional theory (DFT) based method with hybrid B3LYP functional. 6-31G(d,p) basis has been used throughout the calculations, whereas for the metal LanL2DZ basis set has been applied. The phosphorescence energy has been estimated as the energy difference at the minima of S 0 and T 1 states, respectively.  E(T 1 -S 0 ) = 1.93 eV (642 nm)  E(T 1 -S 0 ) = 2.43 eV (510 nm) In both prepared complexes, the nap ligand coordinates with both N atoms to the metal centre in a bidentate manner. Whereas in the solid state structure of the Re complex the metal nitrogen distances are identical [2.232(3) and 2.236(2) Å], the nap is highly asymmetrically coordinated in the Cu compound [2.025(2) vs (11) Å]. Both complexes exhibit a broad phosphorescence in solid state at T = 300 K (Re: em = 594 nm; Cu: em = 638 nm), which is a blue shift compared to the phen counterpart (Re: em = 620 nm; Cu: em = 700 nm). [1,3] No luminescence is detected in solution at room temperature. The crystal structure of the Re complex is accurately reproduced by the DFT calculations. In contrast, the experimental and calculated geometries of the Cu complex show significant differences. The same is true for the calculated energy differences  E(T 1 -S 0 ) compared to the measured emission wavelength. The DFT calculations confirm the MLCT character of the triplet state T 1, thus the emissions are attributed to a 3 MLCT state. [(nap)Cu(DPEPhos)]PF 6 (nap)Re(CO) 3 Cl [(nap)Cu(DPEPhos)] + free ligand (nap)Re(CO) 3 Cl