A series of as-tnazmes contammg the cuprome functlonal group 1s achieved by mcorporatmg a methyl substltuent adjacent to the mnne nitrogen of highly sensltwe ferrom-yleldmg as-tnazmes These are much more readdy prepared than most cuprome reagents The chelation and chromogemc properties of these cuprome compounds m reaction with copper(I) have been mvestlgated spectrophotometncally Spectral data, condlfions favourable for chelate formation and other data are reported The results demonstrate that the effect of different substltuents at the S-and 6-posltlons of 3,5,6-tnsubstltuted 1,2,4-tnazmes towards the enhancement of chromophonaty of the cuprome functional group LS almost identical except for the Zfuryl substltuents The compound 3_(6-methyl-2-py)_5,6-b&2-fury&as-tnazme (Pm) 1s supenor m senslttnnty to all cuprome-type chromogens previously reported The copper(I) complex of PFT is extractable by chloroform and n-hexanol as a perchlorate ion assoclatlon complex Hrlth appreciable enhancement m sensltwlty Keywords Spectrophotometry, Chromogens, Cuprome compounds, Tnazmes The sensltlvlty and selectrvlty of an organic reagent towards metal Ions can be modlfled to a great extent by mcorporatmg different substltuents m the molecule An example 1s the development of the ferrom-and cuprome-type of compounds as highly sensitive and selectwe reagents for the spectrophotometnc determmatlon of lron(II) and copper(I) [l-3] Cluomophores of the cuprome-type are dlstmgmshed Correspondence to WI Stephen, School of Chenustry, Umverslty of Bummgham, Edgbaston, Bummgham B15 2lT (UK) by the presence of the bldentate chelate functional group ~c.-__c@ 'C=N' X' 'NE& 'X commonly known as the cuprome functional group and have found Hrlde apphcatlon as highly selective reagents for the spectrophotometnc determmatlon of copper(I) Examples are 2,2'blqumohne (E = 6220 1 mol -I cm-' at 546 nm) [4,5], 2,9-dlmethyl-l,lO-phenanthrolme (neocuprome, E = 7950 1 mol-' cm-') at 545 mn) [6,7], 2,9-dnnethyl-4,7-dlphenyl-l,lO-phenanthro-