1,8-Diamino-3,6,10,13,16,19-hexaazabicyclo(6,6,6)eicosane 3,6,10,13,16,19-Hexaazabicyclo(6.6.6)eicosane-1,8-diamine 91002-72-1 Diamsar Diamsar chelate NH2-Sar-cage