Developing the {M(CO)₃}⁺ Core for Fluorescence Applications:  Rhenium Tricarbonyl Core Complexes with Benzimidazole, Quinoline, and Tryptophan Derivatives

Abstract

Tridentate ligands derived from benzimidazole, quinoline, and tryptophan have been synthesized, and their reactions with [NEt4]2[Re(CO)3Br3] have been investigated. The complexes 1-4 and 6 and 7 exhibit fac-{Re(CO)3N3} coordination geometry in the cationic molecular units, while 5 exhibits fac-{Re(CO)3N2O} coordination for the neutral molecular unit, where N3 and N2O refer to the ligand donor groups. The ligands bis(1-methyl-1H-benzoimidazol-2-ylmethyl)amine (L1), [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 (L3), [bis(quinolin-2-ylmethyl)amino]acetic acid methyl ester (L4), 3-(1-methyl-1H-indol-3-yl)-2-[(pyridin-2-ylmethyl)amino]propionic acid (L5), 2-[bis(pyridin-2-ylmethyl)amino]-3-(1-methyl-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.NEt4Br . 8.5H2O (3(2).NEt4Br . 8.5H2O), [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) A, b = 16.1292(7) A, c = 10.2689(4) A, beta = 99.353(1) degrees , V = 2154.8(2) A3, Z = 4. Crystal data for C56H73Br3N11O18.50 Re2 (3(2).NEt4Br . 8.5H2O): monoclinic, C2/c, a = 34.7760(19) A, b = 21.1711(12) A, c = 20.3376(11) A, beta = 115.944(1) degrees , V = 13464.5(1) A3, Z = 8. Crystal data for C26H21BrN3O5Re (4): monoclinic, P2(1)/c, a = 16.6504(6) A, b = 10.1564(4) A, c = 14.6954(5) A, beta = 96.739(1) degrees , V = 2467.9(2) A3, Z = 4. Crystal data for C27H24BrN4O5Re (6): monoclinic, P2(1), a = 8.7791(9) A, b = 16.312(2) A, c = 8.9231(9) A, beta = 90.030(1) degrees , V = 1277.8(2) A3, Z = 2.

A Novel Organometallic ReI Complex with Favourable Properties for Bioimaging and Applicability in Solid‐Phase Peptide Synthesis

“…[31] At exactly the same concentrations of 5 we observed an increase in fluorescence intensity of only about www.chembiochem.org 5 % on switching from non-degassed to degassed acetonitrile ( Figure 3). Complex 5 is thus less sensitive to quenching processes caused by the presence of dissolved dioxygen.…”

“…Most luminescent rhenium complexes with potential imaging applications contain the fac-Re(CO) 3 core and are based on bisimine ligands such as bipyridine or phenanthroline [26][27][28][29][30] or on tridentate chelates such as bis(pyridylmethyl)amine or bis(quinolinylmethyl)amine. [31][32][33][34][35][36] Here we report on the synthesis, characterization and photophysical behaviour of a novel chelating tridentate ligand based on bis(phenanthridinylmethyl)amine (bpm), its rhenium complexes and peptide conjugates. The complexes described below have more favourable photophysical properties than the above ligand systems.…”

Photoluminescent properties of heteroleptic cyclometalated platinum(II) complexes bearing 1,3-bis(3,4-dibutoxyphenyl)propane-1,3-dionate as an ancillary ligand

“…Organometallic complexes with heavy metal centers have received considerable attention in recent years because their high phosphorescence quantum efficiencies offer significant advantages in a variety of applications, such as organic light-emitting diodes (OLEDs) [1,2], oxygen sensors [3][4][5], and bio-labeling materials [6,7]. For OLED application, cyclometalated iridium(III) complexes involving homoleptic Ir(C 4 N) 3 and heteroleptic (C 4 N) 2 Ir(O 4 O) complexes have been widely studied (C 4 N and O 4 O are 2-arylpyridinate and 1,3-diketonate ligands, respectively) [8,9].…”

Functionalised Tris(pyrazolyl)methane Ligands and Re(CO)3 Complexes Thereof

“…[1][2][3] Several groups are developing ligands for the radio-labelling of bio-molecules. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Many of these ligating moieties are based upon bis(pyridylmethyl)amine derivatives and we have also developed a N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer with bis(pyridylmethyl)amine derivatives as metal binding sites. [19] Another class of widely used ligands in coordination chemistry and organometallic chemistry are the tris(pyrazolyl)borates (Tp), developed by Trofimenko in the early sixties.…”