Color of charge-transfer complexes Charge-transfer complex

-


fig. 1 i2•pph3 charge-transfer complexes in ch2cl2. left right: (1) i2 dissolved in dichloromethane - no ct complex. (2) few seconds after excess pph3 added - ct complex forming. (3) 1 minute later after excess pph3 added, ct complex [ph3pi]i has been formed. (4) after excess i2 added, contains [ph3pi][i3].


many metal complexes colored due d-d electronic transitions. visible light of correct wavelength absorbed, promoting lower d-electron higher excited state. absorption of light causes color. these colors quite faint, however. because of 2 selection rules:



the spin rule: Δ s = 0

on promotion, electron should not experience change in spin. electronic transitions experience change in spin said spin-forbidden, such in spin forbidden reactions.



laporte s rule: Δ l = ± 1

d-d transitions complexes have center of symmetry forbidden - symmetry-forbidden or laporte-forbidden.


charge-transfer complexes not experience d-d transitions. thus, these rules not apply and, in general, absorptions intense.


for example, classic example of charge-transfer complex between iodine , starch form intense purple color. has widespread use rough screen counterfeit currency. unlike paper, paper used in currency not sized starch. thus, formation of purple color on application of iodine solution indicates counterfeit.








Comments

Post a Comment

Popular posts from this blog

Ancient Laconophilia Laconophilia

-
1 ancient laconophilia 1.1 athens 1.2 philosophers 1.3 contrary views ancient laconophilia athens in ancient athens, laconism began current of thought , feeling after persian wars. some, cimon, son of miltiades, believed athens should ally sparta against persian empire. cimon persuaded athenians send soldiers aid sparta, when helots (serfs of spartans) revolted , fortified mount ithome. spartans sent athenians home again thanks, lest democratic athenian ideas influence helots or perioeci. some athenians, disliked commerce, preferred closed society , rule of few. believed spartan constitution superior own. went far imitate spartan manners going around athens long-haired , unwashed, spartiates. plato s republic, set in 5th century bc, gives credence claim having socrates opine spartan or cretan type of political regime favorite of many . a group of extreme laconising oligarchs, known thirty tyrants, seized power in athens in 404 bc , held eleven months, assisted spartan army. rule, howe...
Read more

Ballysillan and Upper Crumlin Road Crumlin Road

-
ballysillan presbyterian church the ballysillan road leads off crumlin road , major area of loyalist housing. containing likes of silverstream , carr s glen districts, ballysillan road continues far north. circular road in turn links antrim road, began @ carlisle circus. during northern ireland troubles ballysillan noted centre loyalist paramilitary activity , home base of d company of ulster volunteer force (uvf) under command of john bingham along glenbryn, ballysillan @ centre of loyalist feud in 2003 when jimbo simpson, had been ousted head of north belfast brigade of ulster defence association (uda), attacked number of houses in area part of failed attempt retake control of brigade , force out replacement william borland. crumlin road entrance ballysillan houses historic church, ballysillan presbyterian church. due elevated , exposed location ballysillan, takes name irish language expression meaning townland of willow grove , 1 of coldest areas of city during winter. ballysilla...
Read more

Benefits Al-Anon/Alateen

-
1 benefits 1.1 problems 1.2 improvement 1.3 treatment of alcoholism benefits problems al-anon/alateen literature focuses on problems common family members , friends of alcoholics such excessive care-taking, inability differentiate between love , pity , loyalty abusers, rather problems of alcoholic. organization acknowledges members may join low self-esteem, largely side-effect of unrealistically overestimating agency , control: attempting control person s drinking behavior and, when fail, blaming other person s behavior. improvement participation in al-anon has been associated less personal blame women who, whole, engage in more initial personal blame drinking men. family members of alcoholics begin improve learn recognize family pathology, assign responsibility pathology disease, forgive themselves, accept adversely affected pathology , learn accept family members shortcomings. al-anon members encouraged keep focus on themselves, rather on alcoholic. although members believe changed ...
Read more