Developing the {M(CO)3}+ core for fluorescence applications:: Rhenium tricarbonyl core complexes with benzimidazole, quinoline, and tryptophan derivatives

Tridentate ligands derived from benzimidazole, quinoline, and tryptophan have been synthesized, and their reactions with [NEt4](2)[Re(CO)(3)Br-3] have been investigated. The complexes 1-4 and 6 and 7 exhibit fac-{Re(CO)(3)N-3} coordination geometry in the cationic molecular units, while 5 exhibits fac-{Re(CO)(3)N2O} coordination for the neutral molecular unit, where N-3 and N2O refer to the ligand donor groups. The ligands bis(1-methyl-1H-benzoimidazol-2-ylmethyl)amine (U), [bis(1-methyl-1H-benzoimidazol-2-ylmethyl)amino]acetic acid ethyl ester (L2), [bis(1-methyl-1H-benzoimidazol-2-ylmethy)amino]acetic acid methyl ester (U), [bis(quinolin-2-ylmethyl)amino]acetic acid methyl ester (1-4), 3-(1-methyl-1H-indol-3-yl)-2-[(pyridin-2-ylmethyl)amino]propionic acid (U), 2-[bis(pyridin-2-ylmethyl)amino]3-(1 -meathyl-1H-indol-3-yl)propionic acid (L6), and 2-[bis(quinolin-2-ylmethyl)amino]-3-(1-methyl-1H-indol-3-yl)propionic acid (L7) were obtained in good yields and characterized by elemental analysis, 1D and 2D NMR, and high-resolution mass spectrometry (HRMS). The rhenium complexes were obtained in 70-85% yields and characterized by elemental analysis, 1D and 2D NMR, HRMS, IR, UV, and luminescence spectroscopy, as well as X-ray crystallography for [Re(CO)(3)(L1)]Br (1), {[Re(CO)(3)(L2)]Br}(2)center dot NEt4Br center dot 8.5H(2)O (3(2)center dot NEt4Br-8.5H(2)O), [Re(CO)(3)(L4)]Br (4), and [Re(CO)(3)(L6)]Br (6). Crystal data for C21H19BrN5O3Re (1): monoclinic, P2(1)/c, a = 13.1851(5) angstrom, b = 16.1292(7) angstrom, c =: 10.2689(4) A, beta = 99.353(1)degrees, V = 2154.8(2) angstrom(3), Z = 4. Crystal data for C56H73Br3N11O18.50Re2 (3(2)center dot NEt4-Br center dot 8.5H(2)O): monoclinic, C2/c, a = 34.7760(19) angstrom, b = 21.1711(12) angstrom, c = 20.3376(11) angstrom, beta = 115.944(1)degrees, V = 13464.5(l) angstrom(3), Z = 8. Crystal data for C26H21BrN3O5Re (4): monoclinic, P2(1)/c, a = 16.6504(6) angstrom, b = 10.1564(4) angstrom, c = 14.6954(5) angstrom, beta = 96.739(1)degrees, V = 2467.9(2) angstrom(3), Z = 4. Crystal data for C27H24BrN4O5Re (6): monoclinic, P2(1), a = 8.7791(9) angstrom, b = 16.312(2) angstrom, c = 8.9231(9) angstrom, beta = 90.030(1)degrees, V = 1277.8(2) angstrom(3), Z = 2.