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Deprotonating melamine to gain highly interconnected materials: Melaminate salts of potassium and rubidium

: Görne, Arno; Scholz, Tanja; Kobertz, Dietmar; Dronskowski, Richard


Inorganic Chemistry 60 (2021), No.20, pp.15069-15077
ISSN: 0020-1669
ISSN: 1520-510X
Journal Article
Fraunhofer IKTS ()
graphitic carbon nitride; light; adduct; sodium; complex; guanidine; thermal condensation; crystal-structure; total-energy calculations; bilbao crystallographic server

A new class of materials, melaminate salts of potassium and rubidium, has been obtained by deprotonating molecular melamine in liquid ammonia. Potassium melaminate KC3N6H5 center dot NH3 and rubidium melaminate RbC3N6H5 center dot 1/2NH(3) were characterized by single-crystal XRD, showing that the melaminate anion is slightly distorted compared to the neutral molecule due to the ionic imine group, but it still forms extensive hydrogen bonding networks. The melaminate anion also displays an increased coordination ability of mu(4) and mu(6+1) (the maximum for melamine is mu(3)). Thermal gravimetry coupled with mass spectrometry evidence a multistep decomposition with liberation of ammonia first and then cyanamide and larger fragments. A plausible decomposition mechanism is proposed. The infrared spectrum allows to identify the fingerprint of the melaminate vibrations such as to partially characterize the also synthesized amorphous sodium melaminate NaC3N6H5 center dot nNH(3) and the proposed tripotassium melaminate K3C3N6H3.