Polyhedron Vol[ 06\ Nos[ 14\ 15\ pp[ 3392Ð3302\ 0887 Þ 0887 Elsevier Science Ltd  Pergamon All rights reserved[ Printed in Great Britain 9166Ð4276:87 ,08[99¦9[99 PII] S9166Ð4276"87#99132Ð4 Potentiometric and spectroscopic studies of the copper"II# complexes with some aminodiphosphonic acids in aqueous solution Barbara Kurzak\ a  Anna Kamecka\ a Krzysztof Kurzak\ a Julia Jezierska b and Pawe< Kafarski c a Institute of Chemistry\ Pedagogical University\ 97!009 Siedlce\ Poland b Faculty of Chemistry\ University of Wroclaw\ 49!272 Wroclaw\ Poland c Institute of Organic Chemistry\ Biochemistry and Biotechnology\ Technical University\ 49!269 Wroclaw\ Poland "Received 16 March 0887^ accepted 04 June 0887# Abstract *The stoichiometries and stability constants of the copper"II# complexes with seven amino! diphosphonates ðRÐN"CH 1 PO 2 H 1 # 1 \ LŁ containing iminomethylenephosphonate moieties have been deter! mined pH!metrically at 14>C and at an ionic strength of 9[19 mol dm −2 "KCl#[ The results suggest for L0Ð5 only equimolar species] ðCu"H 1 L#\ ðCu"HL#\ ðCuLŁ and two hydroxo ðCuH −0 LŁ and ðCuH −1 LŁ\ in the pH range of 1Ð00[4\ the only di}erence is the presence of an additional ðCu"H 2 L#Ł species "½04)# at low pH for N!2! picolyliminodi"methylenephosphonic# acid[ For L6 the model contains protonated and non!protonated 0]1 species[ From the comparative analysis of the stability and the spectroscopic "UVÐVIS and EPR# data it has been established that the ligands in ðCuHLŁ and ðCuLŁ are tridentate^ the formation of two _ve!membered chelate rings leads to very stable complexes[ The LMCT bands from O − "PO 2 1− # and N imino to Cu 1¦ are at 114Ð 120 and 291Ð166 nm[ Þ 0887 Elsevier Science Ltd[ All rights reserved Keywords] potentiometry^ stability constants^ copper"II# complexes^ aminopolyphosphonates^ EPR spectra^ UVÐVIS spectra[ ——————————————————————————————————————————————— INTRODUCTION The aminopolyphosphonates are analogues of ami! nopolycarboxylates in which the carboxyl groups "CO 1 − # are substituted by phosphonate moieties "PO 2 1− #[ Among the most widely commercially used of aminoalkylphosphonic acids ð0Ð4Ł is diethylene! triamine ! N\N\N?\Ný\Ný ! pentamethylenephos phonic acid^ available under various trade names such as {{DEQUEST|| and {{BRIQUEST||[ An investi! gation of the interaction of the phosphonic groups with metal ions may provide useful information on the behaviour of these type of compounds[ Studies on  Author to whom correspondence should be addressed[ Fax] ¦3714!33!19!34^ E!mail] bkurzakÝwsrp[siedlce[pl 3392 the simpler aminomethylenephosphonic acids serve as models for understanding the behaviour of more complex systems ð5Ł[ Aminopolyphosphonic acids and their derivatives have also received considerable attention because of their interesting biological activity[ For example\ N\N?!di"phosphonomethyl#glycine is an active com! ponent of Polaris þ \ known plant growth regulator ð6Ł\ whereas N!"phosphonomethyl#glycine is an active ingredient of a popular herbicide Roundup þ ð7\ 8Ł[ Metal aminophosphonate "aminopolyphos! phonate# chemistry is attracting increasing interest because of the variety of properties than can be intro! duced via the phosphonate ligand ð09\ 00Ł[ The com! plex!formation equilibria have been reported for several kinds of C! or N!substituted derivatives of iminodimethylenebis"phosphonic acid# ð01Ð05Ł[ The