The Influence of the Amide Linkage in the Fe(III) -Binding Properties of Catechol-Modified Rosamine Derivatives.
The two new fluorescent ligands RosCat1 and RosCat2 contain catechol receptors connected to rosamine platforms through an amide linkage and were synthesized by using microwave-assisted coupling reactions of carboxyl- or amine-substituted rosamines with the corresponding catechol units and subsequent deprotection. RosCat1 possesses a reverse amide, whereas RosCat2 has the usual oriented amide bond (HNCO vs. CONH, respectively). The ligands were characterized by means of NMR spectroscopy, mass-spectrometry, and DFT calculations and X-ray crystallography studies for RosCat1. The influence of the amide linkage on the photophysical properties of the fluorescent ligands was assessed in different solvents and showed a higher fluorescence quantum yield for RosCat1. The coordination chemistry of these ligands with a Fe(III) center has been rationalized by mass-spectrometric analysis and semiempirical calculations. Octahedral Fe(III) complexes were obtained by the chelation of three RosCat1 or RosCat2 ligands. Interestingly, the unconventional amide connectivity in RosCat1 imposes the formation of an eight-membered ring on the chelate complex through a "salicylate-type" mode of coordination.
LAQV-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto (Portugal).
Carla
C
Queirós
UCIBIO-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto (Portugal).
Andreia
A
Leite
UCIBIO-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto (Portugal).
Maria
M
G M Couto
LAQV-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto (Portugal).
Luís
L
Cunha-Silva
Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche (STEBICEF), Università di Palermo, Vialle delle Scienze, Edifício 17, 90128 Palermo (Italy).
Giampaolo
G
Barone
LAQV-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto (Portugal).
Baltazar
B
de Castro
UCIBIO-REQUIMTE, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, 4050-313 Porto (Portugal).
Maria
M
Rangel
UCIBIO-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto (Portugal). ana.silva@fc.up.pt.
André
A
M N Silva
UCIBIO-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto (Portugal). andre.silva@fc.up.pt.
Ana
A
M G Silva
amides; coordination modes; iron; ligand design; mass spectrometry