resumo
A new series of 3D lanthanide (Ln) frameworks has been synthesized with the general formula [{Ln(L)(H2O)}center dot H2O](n) (where Ln = La(1), Tb(2) and Dy(3); L = (HO)OC6H2(CH2COO)(2); H3L = 2,5-dihydroxy-1,4-benzenediacetic acid = DHBDA). All the crystals were analyzed by single crystal X-ray diffraction. The Ln ions are octa-coordinated having the square antiprism geometry with the D-4d symmetry and connected along the crystallographic a-axis forming a zigzag chain. These chains are further connected by the ligands in three-dimensional crystallographic space. Compounds 2 and 3 were subjected to variable temperature magnetic susceptibility measurements and photoluminescence studies. Magnetic studies reveal that compound 2 possesses antiferromagnetic coupling whereas compound 3 shows ferromagnetic interaction at temperatures above ca. 40 K. The emission spectra of compounds 2 and 3 combine the intra-4f emission of the Ln ions with that of the ligand, depending on the selected temperature, pointing out that the energy transfer processes are thermally activated. In addition, compound 2 presented an invariant D-5(4) lifetime behaviour at temperatures between 15 and 300 K. Theoretical analysis showed that the long-lived lifetimes of the free ligand's excited states and the intramolecular energy transfer rate invariability are responsible for such abnormal behaviour.
palavras-chave
METAL-ORGANIC FRAMEWORKS; HYDROTHERMAL SYNTHESIS; TRANSITION-METAL; BUILDING-BLOCKS; SINGLE-CRYSTAL; CARBON-DIOXIDE; MAGNETIZATION; COMPLEXES; DESIGN; CHAIN
categoria
Chemistry, Multidisciplinary; Crystallography
autores
Sen, R; Paul, S; Sarkar, A; Botas, AMP; Neto, ACN; Brandao, P; Lopes, AML; Ferreira, RAS; Araujo, JP; Lin, Z
nossos autores
Albano Neto Carneiro Neto
Investigador Júnior
Alexandre Manuel Pedroso Botas
Bolseiro de pós-Doutoramento
Maria Rute de Amorim e Sá Ferreira André
Professor Catedrático
Paula Cristina Ferreira da Silva Brandão
Investigador Auxiliar
Zhi Lin
Investigador PrincipalGrupos
G1 - Materiais Porosos e Nanossistemas
G2 - Materiais Fotónicos, Eletrónicos e Magnéticos
G3 - Materiais Eletroquímicos, Interfaces e Revestimentos
Projectos
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
SusPhotoSolutions - Soluções Fotovoltaicas Sustentáveis (SUSPHOTOSOLUTIONS)
agradecimentos
R. S. thanks DST-SERB for an ECR grant (ECR/2016/001572). The group at Aveiro acknowledges the support from the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. The group at Porto acknowledges the projects IF/00686/2014, POCI-01-0145-FEDER-029454, and POCI-01-0145FEDER-032527. AMPB and ANCN are thankful for the grant financed by the SusPhotoSolutions project (CENTRO-01-0145FEDER-000005).