A metal-organic coordination compound, wherein the coordination compound comprises at least one divalent lanthanide coordinated by a cyclic organic ligand according to formula (1), wherein · i is larger than 3; and · n is equal to 1, 2, or 3; and · L for each occurrence is independently selected from - divalent cyclic organic groups that can be substituted and that are formed by removing two hydrogen atoms from an organic cyclic molecule that can be substituted, - arylenes, preferably 5- or 6-membered ring aromatic or heteroaromatic group, or - biradical fragments of (formula (AA)) and · X is independently selected for each occurrence from the group of (formula (BB)), · wherein R1 and R2 are hydrogen or any covalently bound substituents being identical or different in each occurrence; and · wherein R1 and/or R2 are at least in 3 occurrences not hydrogen, and · wherein two groups R2 can be covalently linked with each other, thereby forming a further cyclic element, it also being possible that two cyclic organic ligands of formula (1) are covalently linked with each other by one or two divalent linking groups which divalent linking groups are formed of one R1 of each of the two cyclic organic ligands of formula (1) that are covalently linked with each other.