3.3.5
Ek transition metal complex coloured isliye dikhta hai kyunki uske partially filled d-orbitals do energy groups mein split ho jaate hain , aur ek electron lower group se upper group mein jump kar sakta hai ek specific colour ki visible light absorb karke. Jo colour hum DEKHTE hain woh ABSORB kiye gaye colour ka complement hota hai .
Definition d-d transitiond-d transition ek electron ka lower-energy set of d usi metal ion ke andar hota hai. Yeh us photon ki absorption se hota hai jiska energy crystal field splitting Δ o Δ t
Definition Crystal Field Splitting Energy (Δ d degenerate hote hain (same energy). Jab ligands paas aate hain, unke electron pairs metal ke d taraf point karte hain woh upar push ho jaate hain; jo orbitals ligands ke beech mein point karte hain woh neeche push ho jaate hain. Inhi do sets ke beech ka energy gap Δ
Octahedral case:
e g d x 2 − y 2 , d z 2 raised .t 2 g d x y , d y z , d z x lowered .
Intuition Energy ↔ wavelength ↔ colourJab white light solution mein se guzarti hai, bilkul sahi energy ka ek photon absorb ho jaata hai taaki electron t 2 g → e g complementary colour .
Δ
Ligand strength (spectrochemical series, weak→strong):
I − < B r − < C l − < F − < O H − < H 2 O < N H 3 < e n < N O 2 − < C N − < C O Δ λ Metal oxidation state: zyada charge ligands ko paas kheenchta hai ⇒ bada Δ Geometry: Δ t = 9 4 Δ o Transition series mein position (Δ
Common mistake Steel-manned misconceptions"Complex woh colour dikhata hai jo woh absorb karta hai."
Kyun sahi lagta hai: lal gulaab lal dikhta hai, toh "cheez = colour of light" natural lagta hai. Fix: opaque objects reflected colour dikhate hain; ek solution transmitted = white minus absorbed = complementary colour dikhata hai. [ T i ( H 2 O ) 6 ] 3 +
"Bada Δ
Kyun sahi lagta hai: "bada" sunne mein "badi wavelength" jaisa lagta hai. Fix: λ = h c /Δ inverse hai — bada gap ek zyada energetic = chhoti wavelength wale photon ki demand karta hai.
"Saare transition metal ions coloured hote hain."
Kyun sahi lagta hai: zyaatar common wale (C u 2 + , F e 3 + , C r 3 + Fix: d 0 d 10 koi possible d-d transition nahi hoti ⇒ colourless.
Recall Quick self-test (answers chhupao!)
Ek metal ion mein colour ke liye kaun si do cheezein honi chahiye? → ==partially filled d-subshell (d 1 d 9
Agar koi complex orange absorb kare, toh kaisa dikhega? → blue (complement) .
H 2 O C N − λ kam ho jaayegi (stronger field, bada Δ
Recall Feynman: ek 12-saal ke bachche ko samjhaoSocho metal atom mein paanch ek jaisi shelves hain uske tiny electron-balls ke liye. Jab tum chhe magnets (ligands) uske aaspaas push karte ho, kuch shelves thodi upar uth jaati hain. Ab ek electron-ball low shelf se high shelf par jump kar sakta hai — lekin sirf tab jab tum usse exactly sahi "kick" do. White sunlight saari sizes ki colour-kicks ka ek bag hai. Ball woh ek kick pakad leta hai jo shelf-gap ke liye fit hoti hai aur usse jump karne mein use karta hai; woh colour light se gayab ho jaata hai. Toh jab tum bottle ke through dekhte ho, rainbow mein ek colour missing hoti hai — aur bacha hua mix woh colour hai jo tumhe dikhti hai! Jump karne ke liye koi electron nahi (full shelves) ya koi empty shelf nahi? Toh kuch pakda nahi jaata aur liquid saaf rehta hai.
"Ligands Split, Light Splits, You See the Opposite."
Aur gap ke liye: "Strong field, Short wave" (dono hard/short se start hote hain). Aur Δ t = 9 4 Δ o four-ninths for the four-cornered (tetrahedral)."
Zyaatar transition metal complexes coloured kyun hote hain? Ek d-electron ek visible photon absorb karke split d-orbital sets ke beech jump karta hai (d-d transition); jo colour dikhti hai woh absorbed colour ka complement hoti hai.
Splitting energy aur absorbed wavelength ko link karne wala formula? Δ o = h c / λ λ = h c / Δ o
Bada Δ o Chhoti (zyada energetic) wavelength, kyunki λ ∝ 1/ Δ o
[ Z n ( H 2 O ) 6 ] 2 + Z n 2 + d 10
S c 3 + Yeh d 0
[ T i ( H 2 O ) 6 ] 3 + Purple/violet; yeh green-yellow (~500 nm) absorb karta hai, aur hum complement dekhte hain.
Spectrochemical series (weak→strong, key members)? I − < B r − < C l − < F − < H 2 O < N H 3 < e n < N O 2 − < C N − < C O
Stronger ligand ka Δ Bada Δ λ H 2 O → N H 3
Δ t Δ o Δ t = 9 4 Δ o
Octahedral field mein e g d x 2 − y 2 d z 2
Crystal field splitting Δ
