542
Kořínková, Lyčka, Cee, Nádvorník, Jirásko, Hrdina:
is a less flexible com plex with n ew five- an d six-m em bered rin gs, wh ich are
m ore flexible an d, th us, several isom ers existin g in an equilibrium can be
form ed. Molar m agn etic susceptibility data proved th e existen ce th e Co(III)
oxidation state in th e com plexes.
EXPERIMENTAL
Gen eral
Aceton itrile an d m eth an ol for HPLC were purch ased from Sigm a–Aldrich (Prague, Czech
Republic). Water was purified usin g th e Milli-Q plus water purification system (Millipore,
USA). Am m on ium acetate was purch ased from Lach -Ner (Czech Republic). 1H an d 13C NMR
spectra were recorded on a Bruker Avan ce 500 spectrom eter (500.13 MHz for 1H an d
125.76 MHz for 13C) in DMSO-d6. Th e 1H an d 13C NMR ch em ical sh ifts were referen ced to
in tern al TMS. All 2D experim en ts (gradien t-selected gs-COSY, gs-HMQC, gs-HMBC) were
perform ed usin g m an ufacturer’s software. Magn etic susceptibility was m easured at room
tem perature (25 °C) usin g a Variable Tem perature Gouy Balan ce apparatus (Newport In stru-
m en ts, UK) an d Hg[Co(NCS)4] as calibran t. Th e values of m agn etic m olar susceptibility were
corrected by th e Pascal con stan ts19. Positive- an d n egative-ion electrospray ion isation (ESI)
m ass spectra were m easured on an ion trap an alyser (Esquire 3000, Bruker Dalton ics,
Germ an y). Th e full-scan m ass spectra were m easured in th e ran ge m/z 50–1000. Th e sam ples
were dissolved in a water/aceton itrile (1:1) m ixture an d an alysed by direct in fusion at th e
flow rate 5 µl m in –1. Th e ion source tem perature was 300 °C, th e flow rate an d th e pressure
of n itrogen were 4 l m in –1 an d 10 Pa, respectively.
Diazotisation of 2-Am in oph en ol
2-Am in oph en ol (0.02 m ol, 2.18 g; Aldrich ) was m ixed with water (20 m l) an d con cen trated
HCl (5 m l, 35%). Th e obtain ed fin e suspen sion was extern ally cooled un der in ten sive stir-
rin g to 0–5 °C an d 5 M aqueous NaNO2 (5 m l) was slowly added. Th e coolin g was stopped
an d th e suspen sion was stirred at am bien t tem perature (ca. 22 °C) for 20–30 m in un til a
yellow-brown solution of th e diazon ium com poun d was produced. Th e solution was used
for subsequen t couplin g reaction .
Preparation of 3-[(2-Hydroxyph en yl)azo]citrazin ic Acid (2a)
Citrazin ic acid (0.02 m ol, 3.20 g; Aldrich ) was m ixed with water (15 m l) an d 5 M aqueous
NaOH (13 m l) an d th e tem perature was m ain tain ed at 0–5 °C (extern al coolin g). Th e solu-
tion of th e diazon ium com poun d was gradually added un der in ten sive stirrin g. pH was ad-
justed to ca. 8 by th e addition of 5 M aqueous NaOH. Wh en th e couplin g reaction was
com pleted (after ca. 3 h ), pH was adjusted to 4 by th e addition of con cen trated HCl (35%)
an d th e precipitated m on oazo dye was filtered off an d dried at 90–110 °C. Th e yield of
crude dye 2a was 5.84 g (98%). Th e purity of th e dye was determ in ed by TLC (Alugram SIL
G/UV254, Mach erey–Nagel, Germ an y; m obile ph ase: propan -2-ol/propan -1-ol/eth yl acetate/
water 2:4:1:3 (v/v/v/v)). Accordin g to TLC, 2a was pure (RF 0.8). C12H9N3O5 (275): ESI+, m/z:
320.0 [M + 2 Na – H]+, 100%; 301.9 [M + 2 Na – H – H2O]+; 276.0 [M + H]+. ESI–, m/z: 295.8
[M –2 H + Na]–; 273.8 [M – H]–; 255.8 [M – H – H2O]–; 229.8 [M – H – CO2]–, 100%.
Collect. Czech. Chem. Commun. 2009, Vol. 74, No. 4, pp. 535–544