A metal-organic coordination compound, formed of a divalent Europium cation, a macrocyclic organic ligand, and iodide anions in an amount to make the coordination compound electrically neutral, with the macrocyclic organic ligand comprising 16 to 23, preferably 18 to 20 ring atoms in a single macrocycle ring accommodating the divalent Europium, with the exception of macrocyclic organic ligands M1 to M5: wherein the macrocyclic organic ligand has the formula: with • n being 4 to 6; more preferable 6 and • L being independently in each occurrence a divalent organic group formed by removing two hydrogen atoms from an organic molecule containing at least two hydrogen atoms, with ∘ the shortest sequence of atoms in each L between the two linkages of each L with the remainder of the macrocycle in the macrocyclic ligand being 2 to 4, preferably 3 or 4 atoms, and with ∘ one of those 2 to 4, preferably 3 or 4 atoms independently for each L being selected from the heteroatoms B, N, P, S, Se, Si or O, preferably N, S, Se or O, the other atoms in the shortest sequence of atoms being carbon, wherein preferably the heteroatoms in the macrocycle are non-neighboring, and wherein any further ring structures, forming part of the macrocyclic organic ligand in addition to the macrocycle itself are covalently linked with one macrocycle atom, or form part of the macrocycle by 1,2-, 1,3- or 1,4-annelation of the further ring structure to the macrocycle, and are not additionally covalently linked with other atoms of the macrocycle. • n being 4 to 6; more preferable 6 and • L being independently in each occurrence a divalent organic group formed by removing two hydrogen atoms from an organic molecule containing at least two hydrogen atoms, with ∘ the shortest sequence of atoms in each L between the two linkages of each L with the remainder of the macrocycle in the macrocyclic ligand being 2 to 4, preferably 3 or 4 atoms, and with ∘ one of those 2 to 4, preferably 3 or 4 atoms independently for each L being selected from the heteroatoms B, N, P, S, Se, Si or O, preferably N, S, Se or O, the other atoms in the shortest sequence of atoms being carbon, wherein preferably the heteroatoms in the macrocycle are non-neighboring, and wherein any further ring structures, forming part of the macrocyclic organic ligand in addition to the macrocycle itself are covalently linked with one macrocycle atom, or form part of the macrocycle by 1,2-, 1,3- or 1,4-annelation of the further ring structure to the macrocycle, and are not additionally covalently linked with other atoms of the macrocycle. ∘ the shortest sequence of atoms in each L between the two linkages of each L with the remainder of the macrocycle in the macrocyclic ligand being 2 to 4, preferably 3 or 4 atoms, and with ∘ one of those 2 to 4, preferably 3 or 4 atoms independently for each L being selected from the heteroatoms B, N, P, S, Se, Si or O, preferably N, S, Se or O, the other atoms in the shortest sequence of atoms being carbon, wherein preferably the heteroatoms in the macrocycle are non-neighboring, and wherein any further ring structures, forming part of the macrocyclic organic ligand in addition to the macrocycle itself are covalently linked with one macrocycle atom, or form part of the macrocycle by 1,2-, 1,3- or 1,4-annelation of the further ring structure to the macrocycle, and are not additionally covalently linked with other atoms of the macrocycle.